AMER. ZOOL., 37:260-268 (1997)
Life Before Model Systems: General Zoology at August Weismann's
Institute1
FREDERICK B. CHURCHILL
Department of the History and Philosophy of Science,
Indiana University, Bloomington, Indiana 47405
With the current interest in and criticism of Model Systems Research
in mind, I review some of the details of a research program at the turn of the
century. I present data about career trajectories of the degree recipients in August
Weismann's Institute of Zoology, in Freiburg i/Br., Germany. I ennumerate the
organisms they use in their research and provide some discussion about the level
of analysis performed by certain students bound for academic careers. I conclude
that between 1880 and 1912 diversity prevailed in career objectives, research projects, organisms investigated and levels of analysis. This was the diversity of a
General Zoology suited to Weismann's primary interests in evolution and the contemporary expectations of academic zoology. This General Zoology contrasts with
the organism specific research prevalent at the same institute directed by Hans
Spemann between 1918 and 1931. In closing I propose a sequence of historical
stages which changed the General Zoology at the beginning of the current century
into Model Systems Research at the end.
SYNOPSIS.
During the past century biology has
made enormous strides by in-depth studies
of a few organisms. In popular imagination
the white mouse, the fruit fly, the guinea
pig, field corn and now the zebrafish have
been partners and martyrs to our advances.
More sophisticated in their perspective of
events, professional biologists also enumerate Neurospora, E. coli, Xenopus, Arabadopsis and scores of other organisms, which
serve as research subjects for the working
out of functional, genetic and developmental problems.
The degree to which biologists can generalize their research results beyond the exemplary species plucked from nature's multitude has always been a controversial matter, but in this age of high-tech biology and
high cash commitments to medical research
it is increasingly tempting to confer on exemplars of given functions the status of universal models. The claim being made
through such a tactic is a cognitive one, that
is, that a chosen species, or a domesticated,
standardized sub-population of that species,
may serve as a microcosm of an important
segment of the organic macrocosm. The
successful conferral of model system status,
however, has inevitable repercussions on
both the training and research sides of a biology program.
Both the cognitive and institutional roles
of what is now referred to as model systems
biology, form the focus of a number of recent discussions. Microbiologist Howard
Gest has questioned the "Rosetta Stone"
mentality that has driven many biologists to
espouse model systems (Gest, 1995). He reminds us of and endorses what Hans Krebs
once called the "[August] Krogh principle," named after the famous Danish physiologist, who wrote that "For a large number of problems there will be some animal
of choice or a few such animals on which
it can be most conveniently studied"
(Krebs, 1975; Krogh, 1929, p. 247). Krogh
thereby implied that convenience, in a
broad sense, and specific problem solving,
not a presumptive general model, had and
should guide the choice of an organism in
research (Gest, 1995). Developmental bi1
From the Symposium Forces in Developmental Bi- ologist Jessica Bolker has provided a
ology Research: Then and Now presented at the An- thoughtful analysis of some of the shortnual Meeting of the Society for Comparative and In- comings of a model systems approach: the
tegrative Biology, 26-30 December 1995, at Washing- unavoidable biases in the organism selecton, D.C.
260
GENERAL ZOOLOGY
tion process, the confusion of experimental
convenience for universality, and a frequent
disregard of phylogenetic reality are among
the dangers she discusses (Bolker, 1995).
Historian Larry Holmes, who examined
Krogh's original invocation within an historical sketch of the use of the frog as a
common research organism, put the question most succinctly when he observed that
"Throughout the history of biological investigation, however, the question of how
far one can extend conclusions drawn from
particular organisms to other organisms (often most crucially to humans) has remained
problematic" (Holmes, 1993, p. 313; see
also Burian, 1993).
My paper represents the flip side of these
discussions. I propose to examine a zoological research program at the end of the nineteenth century, in which there was no consideration of model systems, in part because
that claim would have been antithetical to
the very essence of the program. I do not
wish to imply that the zoology of the twenty-first century should emulate the past, but
an historical excursion can sometimes provide a lens through which we can more critically examine a contemporary issue.
First, I should say some general words
about my interests. For a number of years
the late Professor Helmut Risler and I have
been examining in some detail the zoological institute in Freiburg, which between
1870 and 1912 was directed by August
Weismann. By reading letters and collecting
promotion Gutachten, we have assembled a
good picture of this institution where research claims were being pursued, lives
shaped, aspirations filled—or in some
cases, not filled. Here I propose to examine
whether or not research at that institute represented a unified program, and with these
considerations Weismann's own research
trajectory is relevant for but should not be
equated with the institute. After all, there
were other Dozenten, and a number of assistant professors who inspired students, developed techniques, and helped frame and
answer scientific questions. Nonetheless,
Weismann set the intellectual tone and, as
one of the most distinguished evolutionary
biologists in turn-of-the-century Germany,
he determined the agenda for the institute
261
as a whole. The zoology pursued was Weismann's zoology and many of the individual
research projects were suggested by him.
FREIBURG ZOOLOGICAL INSTITUTE
Weismann took charge of the "zoological institute" and its collections in 1867. At
that time, it was affiliated with the medical
faculty and was little more than an institute
in name. It provided the medical faculty
with courses in comparative anatomy and
embryology, in parasitology and laboratory
training in zoology (zootomisches Practicum). In 1873 the Lehrstuhl for zoology
and the institute were transferred to the
Philosophical Faculty, and only then did
Weismann begin holding his famous lecture
course on the theory of evolution, which
eventuated in his Vortrdge der Descendenztheorie of 1902 (Weismann, 1902;
Nauk, 1954, 1956).
For ten years after the transfer to the
Philosophical Faculty, Weismann's physical
setup changed little; that is, he and his students worked in two cramped rooms on the
fourth floor of the "Old University." Only
after the University of Munich attempted to
hire him away in 1884, could he finally extract from the cultural ministry a new twostory building. This opened its doors two
years later when Weismann was at the
height of his creative powers. Three years
later the state finished the neighboring single-storied building to house the zoological
collections, and in 1907 it completed a 240seat lecture hall, which joined the two older
buildings. By the time of Weismann's inaugural lecture of the winter semester of
1907/1908, student demand required the
university install an additional 100 seats
(Kohler, 1957).
During Weismann's forty-five year tenure
as director of the zoological institute, its
function had changed from providing pedagogical services for the medical school to
a zoological research institute first in the
Philosophical Faculty, and later in the Faculty of Natural Sciences and Mathematics.
Similar growth patterns occurred with other
zoological institutes in Wilhelmine Germany, most of which were liberating themselves from the stranglehold of human anatomy (Nyhart, 1995). The pattern in Frei-
262
FREDERICK B. CHURCHILL
TABLE 1. Frequency of degrees granted to core students in five year increments, the annual average of
all degrees during those increments, and the percentage change.
Five year
increments
1880-1884
1885-1889
1890-1894
1895-1899
1900-1904
1905-1909
1910-1912
Total:
Number of degrees Average of % change from
Ph.D. & Hab both per year preceding period
8
7
2
7
8
17
10
59
+
+
+
+
+
+
+
+
1
1
2
0
2
1
1
8*
1.8
1.6
0.8
1.4
2.0
3.6
3.6
-11.1
-50.0
75.0
42.0
80.0
00.0
* Six of the sixty-one core students received their
doctorates and habilitated at the Freiburg Institute,
bringing the total number of degrees to sixty-seven.
burg was particularly dramatic, for it occurred with an expansion and elevation in
prestige of the university itself, from a marginal to one of the most prominent second
tier universities in the German empire. By
the first decade of the twentieth century, the
University in Freiburg had achieved a par
with the University at Heidelberg, the other
University in the State of Baden (Riese,
1977).
This overall pattern indicates the degree
to which zoological institutes in Germany
in general and Freiburg in particular were
situating themselves not only to produce
knowledge and service the zoological interests of the university, but also to train Doctoranten and Dozenten. It is to these latter
I wish to turn to present certain demographic profiles and to suggest how these might
speak to the current interest in model systems.
Two PROFILES OF CORE STUDENTS
In our survey of university documents
and dissertations between 1880 and 1912,
we have been able to establish a core of 61
Doctoranten and Dozenten in zoology, who
collectively provide a group that I will call
the "core degree students" at the institute.
The following two tables present useful demographic profiles of these and other students at Weismann's institute.
Table 1 indicates the frequence of degrees granted to core students, chronologically ordered. The general trend and the
short term decrease in core students in
TABLE 2. Variety of career choices of all degree recipients, including core students at the Zoological Institute and Ph.D. recipients from the Anatomy Institute.
Career choices
University zool/anat
University other
Explorer naturalist
Museum employment
Professional zoologist
Secondary teacher
Died in WWI
Unknown
Total of career choices
Number of
graduates
17
7
7
9
11
2
1
21
75*
% of total
number of
career choices
22.7
9.3
9.3
12.0
14.7
2.7
1.3
28.0
100.0
* Since a few of the students had multiple careers,
there are more total career choices than degree recipients.
1890-1894 parallels the enrollment curve
in the philosophical faculty and at most
German universities. During the period of
dramatic rise between 1905 and 1909 there
was an increase in overall enrollment at
Freiburg of 27.6% (Riese, 1977).
Tracing the post-graduate careers of
many of the PhD students is a difficult and
time consuming undertaking (Table 2).
Since there is no systematic way of identifying either secondary school teachers or
early deaths, particularly in World War I,
this might explain why so many former students (28%) have disappeared from sight.
This group of missing students, so to speak,
is unlikely to include many university or
technical high school (Technische Hochschule) academics. Of those students whose
career path can be positively identified, a
surprising number of doctoral students
(22.7%) pursued academic careers, either
by habilitating in zoology in Freiburg, by
moving to another zoology or anatomical
research institute in Germany in order to
habilitate, or by entering academic systems
outside of Germany. A smaller number
(9.3%) entered other academic fields, such
as geology or physics.
The third largest group (14.7%) consisted
of non-academic, professional zoologists. I
include in this group individuals who wrote
an occasional zoological paper, but who did
not seem to have an academic affiliation
with a traditional university or technical
university. Also included in this group are
GENERAL ZOOLOGY
former students who became involved in
governmental or industrial research.
Museums offered an important source of
employment (12%) for students with the
Ph.D. in Zoology. Frequently overlapping
with museum work as a profession was a
career trajectory that began with field collecting and exploration overseas, often in
the new German colonies (9.3%).
RESEARCH ORGANISMS AT THE INSTITUTE
It is my belief that these student profiles
(chronological frequency and career trajectories) provide some perspective on, though
not necessarily an explanation for, the varied pattern of research projects pursued at
the insitute. To begin with, the array of organisms that students investigated strikes
the late twentieth century eye as astounding. Three classes of vertebrates, one class
of echinoderms, arthropods of all descriptions with over 300 different species involved, and a scattering of polychaetes,
nematodes, flatworms, coelenterates, and
sponges all came through the doors; many
were kept for study over periods of months,
maybe for a few years, and sometimes
through many generations until the student
completed his or her dissertation. This, of
course, meant aquaria, cages, cold chests,
and rearing pens. It ultimately required conveniently accessible collection storage.
From this it seems self-evident that Weismann and his students operated within the
context of a general zoology concerned
with morphological and phylogenetic questions that depended on cross-type comparisons. Weismann's own research and writings almost always carried the same thrust.
Comparative anatomy, embryology, and cytology were the essence of most research
projects.
If we look more closely at the array of
organisms studied, we note that eight dissertations dealt with vertebrates, but only
two of these were done by core zoology
students. The other six dissertations on vertebrates were written by foreign students
working in the anatomy institute directed
by Weismann's brother-in-law, Robert
Wiedersheim. Instead of receiving M.D.S
however, they chose to collect Ph.D.s on the
basis of Weismann's recommendation to the
263
Philosophical Faculty. This contrast implies
a division of labor in Freiburg between the
two institutes: vertebrates in anatomy
through the medical faculty and invertebrates in zoology through the philosophical
faculty.
Another observation on the array of invertebrates investigated at the institute is
worth reporting. Forty-one of the dissertations and three of the seven Habilitationsschriften concerned questions having
to do with insects or crustaceans—generally, but not always, in a comparative mode.
This makes sense for a number of reasons.
Weismann carried out extensive comparative studies and experiments on butterflies;
his renowned butterfly collection and his
temperature induced variation experiments
on lepidopterans were the direct results of
questions he had about seasonal and sexual
dimorphism, range of variations, and mimicry. Although these questions had strong
developmental and hereditary implications,
they were ultimately designed with Weismann's own evolutionary arguments in
mind. Weismann had also extensively studied crustaceans, particularly the cladocerans
and copepods of the Bodensee, and his and
Chiyomatsu Ischikawa's microscopic studies of reduction division were done largely
on this group of arthropods. For the students in the institute the techniques of preservation and study of insects and the collections were largely in place for their own
research problems. Despite this concentration on insects and crustaceans no one
would have spoken of any group, let alone
a single species, as a model system. Of the
73 different research projects only 20 were
focused on single species. Weismann was
constantly asking, and forcing his students
to ask, about the cross-taxon generality of
any phenomenon he or they might be investigating.
One may point to one exception to this
pattern and that is the work done by Wilhelm Paulcke and Alexander Petrunkewitsch on the domesticated honey bee, Apis
mellifer (Paulcke, 1900; Petrunkewitsch,
1901, 1902). The work was strongly encouraged by Weismann who over a ten year
period was led into an extended reexamination of the production of drones by the
264
FREDERICK B. CHURCHILL
Darmstadt teacher, publisher and beekeeper
Ferdinand Dickel (Churchill, 1974). The
latter had claimed to have repudiated the
long accepted belief, first put forward by
Johannes Dzierzon in the 1840s, that drones
were the products of parthenogenesis. The
institute's studies supported Dzierzon's
claim. If Dickel had been correct, and initially Weismann hoped he was, the studies
would have lent support to a developmental
rather than a particulate explanation of sex
determination. (In Weismannian terminology this would have indicated the germinal
selection of all sex "Determinants" rather
than the action of a single "Determinant.")
Whatever the outcome, we find in this affair
more than one student pursuing a well delimited problem with the same organism.
Much came out of this focused research. Investigators from other institutes contributed
briefly to the scientific exchange; the Dzierzon theory was reconfirmed using the most
up-to-date histological techniques; Petrunkewitsch improved a fixative that became a
standard reagent in microscopy, and Weismann was denied a possible demonstration
of a developmental determination of sex. It
was a short lived episode, and one can hardly speak of the honey bee becoming a model system. No one systematically kept bees
at the zoological institute. In the terms of
Krogh's principle, honey bees were the convenient organism for the study of the production of drones. Today we might consider
the species as an example of sex determination in social hymenopterans, but this is
a modest claim compared with those associated with model systems.
DIVERSITY OF RESEARCH QUESTIONS
Overall, the dissertations and Habilitationsschriften recommended by Weismann
posed a wide diversity of research questions. For a century preoccupied with embryological research it is not surprising to
find that over forty-four or 61% of the seventy-three separate research projects, i.e.,
sixty-seven projects by core students and
six by students in anatomy, had a strong
developmental focus. Despite this commonality their individual research questions
ranged from descriptive studies of development to studies about reproduction, sex-
ual determination, life cycles, and regeneration. Fifteen of these developmental investigations examined in one way or another
the production of gametes, a subject that
was of great interest to Weismann. Only
eight of the developmental projects assumed a recapitulation of specific traits
from ancestral forms, and none that I have
yet read invoked the biogenetic law. A relationship between ontogeny and phylogeny
was always assumed, but Haeckel's fundamental principle did not inspire, let alone
shape, the research program in Freiburg.
Fifteen (<21%) of the projects were anatomical in focus, but as with the developmental projects there was no single
theme. Seven of them were confined to anatomical studies of single organisms (four
of these being done at the anatomical institute); five of the fifteen had comparative anatomical themes and three were what I can
only describe as functional anatomy, i.e.,
making conclusions about function by examining structure and performing simple
and limited experiments. Five other projects
(<7%) were focused on evolution by addressing questions about biogeographical
distribution, convergence, and phylogenetic
lineages of adult structures. Four more
(<6%) dealt primarily with taxonomic
questions; one (<2%) examined the comparative degeneration of structures in related species; one (<2%) can only be described as an experimental study in heredity, and the last two projects (<3%), both
dissertations, were based on literature evaluations in what I might describe as studies
in philosophy of biology. It must be emphasized that many of the dissertations incorporated more than one of these focuses,
and it was not uncommon for a dissertation
to examine development, adult anatomy,
functions of single structures and phylogenetic relationships of several species at the
same time. Generally, however, it was not
difficult to identify a primary focus.
LEVELS OF ANALYSIS
Another noteworthy feature of these research projects is the range in the level of
analysis. It must be emphasized, however,
that many of these monographs switch from
one level to another, but again it is gener-
265
GENERAL ZOOLOGY
TABLE 3. Frequency of various levels of analysis of
sixty zoology dissertations and Habilitationsschriften.
observations arrived at by examining the
thirteen German academic bound zoologists
Number
Level
% of total
(Table 4).
Nothing in Table 4 will be surprising,
Literature analysis
2
3
and I am not even confident that the sample
Organism
7
12
Gross anatomical
16
27
size is large enough to establish any trends,
Tissues and germ layers
14
23
but
I will be brash enough to suggest three,
Cellular
10
17
which
might be relevant to the question of
11
Nucleus and chromosomes
18
the
emergence
of model systems research:
Total:
60
100
1) academic bound zoologists tended during this period to move to deeper levels of
analysis as they went from the dissertation
ally not difficult to ascertain a principle foto the Habilitationsschrift; 2) the deeper
cus. Of sixty monographs that I have been
able to examine with this question in mind, levels of analysis became more common
over time, and 3) only two of the academic
I find the distribution shown in Table 3.
This range of levels again suggests a di- bound zoologists (Petrunkewitsch and
versity in research projects, which implies Schleip) did their dissertations and Habiliin turn a diversity of the instruments and tationsschriften on the same organism, and
techniques routinely used. It might be valu- their research appeared toward the end of
able to examine how this diversity changed our period.
If these trends are real, and an intuitive
over time. It might also be interesting to
guess
based on the reductionist trend of zocorrelate the levels of analysis with students
who took different professional tracks, for ology would suggest they are, they might
this might help us determine how disserta- be explained in a number of, not mutually
tion topics were assigned or sanctioned and exclusive, ways: 1) Research problems and
the extent to which Weismann might have hence hiring patterns, increasingly favored
been involved in career choices. Unfortu- deeper levels of analysis. 2) Increasingly renately, I cannot address these latter two fined equipment and techniques became
questions, but here are some preliminary more commonly available or standard in the
TABLE 4. Changes in the levels of analysis over time and from dissertation to Habilitationsschrift of fourteen
University bound German zoologists.
Habihtationsschnft
Dissertation
Name
5
Gruber
Ziegler
Korschelt
Fritze
Haecker
Spuler
Woltereck
Paulcke
Giinther
Petrunk.
Schleip
Strohl
Demoll
Kiihn
Year
Level
Value"
1878
1882
1882
1889
1889
1892
1898
1899
1900
1900
1906
1907
1907
1908
0
gr
org
tis
0
gr
n
n
tis
n
n
gr
tis
n
0
2
1
3
0
2
5
5
3
5
5
2
3
5
R/A"
2.0
1.5
2.0
2.0
2.6
3.0
3.0
3.25
3.4
3.3
3.2
3.4
Year
Level
Value
R/A
1880
1884
1885
1893
1892
1896
1902
1901
1902
1902
1907
?
1909
1910
gr/n
0
eel
org
n
0
0
0
n
n
n
0
0
eel
3
0
4
1
5
0
0
0
5
5
5
0
0
4
3.0
3.5
2.6
3.25
3.6
3.8
4.0
4.0
* Values other than 0 are assigned to the level of analysis: 0 = work not done in Freiburg and is not included
in the running average; 1 = focus on the whole organism (org); 2 = focus on the gross anatomical or organ
level (gr); 3 = focus on the tissues (tis); 4 = focus on cells (eel); 5 = focus on the nucleus (n).
b
R/A = Running Average.
c
As a protozoologist Griiber worked at both the level of the whole organism and the nucleus simultaneously,
giving his Habilitationsschrift a value of 3 or (1 + 5)/2.
266
FREDERICK B. CHURCHILL
institute over time. 3) Weismann entrusted
analysis on the deeper levels to his better
and more advanced students. It is worth
noting that Weismann's own research had a
more complex chronological profile. During the thirty-four year period covered in
Table 4, it moved in an erratic way with
respect to the level of analysis and generally in the opposite direction suggested in
the table. Weismann completed his studies
of germ cell migrations by 1883; he performed, with the assistance of Ischikawa,
polar body and reduction division work in
the mid 1880s, and by the 1890s he was
writing largely theoretical texts and doing
detailed research on mimicry and induced
coloration on the organism level. His research options were often responses to his
recurring retina problems, which kept him
from pursuing extended microscopic studies.
CONCLUSIONS: MODEL SYSTEMS AND
GENERAL ZOOLOGY
What are the implications of these historical data for contemporary discussions of
model systems?
First, I am struck by the repeated manifestations of diversity in so many aspects of
the operation of the zoological institute in
Freiburg. There was in Weismann's day a
diversity in the life trajectories of the students, an enormous range of research organisms, a multitude of different research
themes, and an even-handed attention to
many levels of analysis, which in turn implied a diversity of techniques and instruments. Many students had very different
goals in research and careers than that
which Weismann may have harbored for the
very best. Their individual desires were encouraged and accommodated within the
framework of a general zoology program. I
suspect that many of these forms of diversity would be antithetical to the more focused research arising from the exploitation
of a single organism and a model systems
agenda.
Second, I have only hinted at the relationship between Weismann's own research
and those of his students, but I am confident
that this was more complex than the traditional stereotype of a Geheimrat Professor
parcelling out segments of his research program to students who simply did the menial
tasks. The impression of the research projects at Weismann's institute emphasizes the
past interest in the variety of life's phenomena and so indicates a collective concern
about all of the processes of evolution, development, and heredity. This breadth
forced a range in methods from taxonomy
to experimental breeding and from biogeography to chromosomal studies.
Third, a common bond between Weismann's and his students' works, however,
can be seen. Weismann's all-encompassing
germ plasm theory, which emerged in the
early 1880s and was the anchor of his research thereafter, and his constant probing
into the complexities of the evolutionary
process set a framework for all the research
done at the institute. Evolution theory in
1900 called for a general zoology that exposed the student to the great diversity in
development, reproduction, morphology,
and geographical distribution of a large
number of organisms. Many a dissertation
would deal with most of these dimensions
to life; so the comparative approach was
imperative.
Fourth, Weismann's general zoology also
mirrored the nature of the academic profession in Germany. To become a successful
academic zoologist, that is, the possessor of
a Lehrstuhl and the director of a zoological
institute, an aspiring candidate was compelled to establish his familiarity with a
wide range of organisms, themes and approaches (Harwood, 1993).
Fifth, it is useful to compare, if only in
passing, Weismann's program with the zoology program pursued when between 1918
and 1931 Hans Spemann became director
of the same Freiburg institute. During this
period his students wrote twenty-four dissertations and five Habilitationsschriften
(FaBler, 1995). Of these only four, or
13.7%, dealt with organisms other than urodeles and anurans, and the vast majority focused exclusively on the salamander Triton.
Collectively these studies opened up a picture of the process of induction in early vertebrate development.
Finally, if "model systems" is going to
be a useful expression in biology, the his-
267
GENERAL ZOOLOGY
torian might consider at least three stages
in the rise of such a strategy: 1) the time
when human and material resources of an
entire institute become mobilized to investigate a specific problem in a single convenient organism; 2) the time when an organism becomes standardized through domestication, in-breeding and selection; and
3) the time when pressures develop for researchers to make cognitive claims about
the universality of their chosen organism.
Significant historical efforts have been
made toward examining the second of these
phases (Kohler, 1994; Clause, 1993; Rader,
1995). To understand better the transformation of the first of these phases, the historian might start with the second decade of
this century when the generation of Spemann, Morgan, and others institutionalized
the in-depth study of given organisms.
I close by noting that when in 1929 August Krogh wrote the passage that was later
enshrined into the principle bearing his
name, he explicitly recommended that in
order to find the correct organism for a
problem, "we [i.e., physiologists] must apply to the zoologists to find them and lay
our hands on them" (Krogh, 1929, p. 247).
He presumably was referring to practitioners of the general zoology tradition so well
exemplified in Weismann's institute. Krogh
and his colleagues had need to hasten, however, because many zoologists, after winning their independence from the medical
faculties in the 1870s and '80s and after
establishing a thriving tradition in general
zoology for the next forty years, were by
the 1920s heading down the same model
systems trail blazed by physiologists.
ACKNOWLEDGMENTS
This lecture has been presented under
variant titles at the University of Minnesota
and Indiana University, and as a memorial
tribute at Johannes Gutenberg University at
Mainz, where comments from listeners
have helped sharpen the paper at many
points. The research has been supported in
part by a German-American Academic
Counsel grant awarded to the author and the
late Helmut Risler of Mainz, Germany for
their joint editorial project entitled August
Weismann: Autobiographien, Dokumente,
Gutachten und Ausgewdhlte Briefe, 2 vols.,
to be published by Freiburg University Library Press.
REFERENCES
Information about students at the zoological institute,
their career trajectories, and their dissertations was
gathered from numerous archival and reference
sources. The most important were the Promotionsakten at the University Archives in Freiburg;
Verzeichnis der Behorden, hehrer, Anstalten,
Beamten und Sludierenden auf der Grossherzoglich Badischen Universitdt Freiburg; Verzeichnis
der Deutschen Hochschulschriften; Deutsches
Biographische Archiv, and the dissertations and
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