270
anatomy of the genus, by Mr. Moss, in the second part of
the ' Linnaean Transactions' for 1870. The mode of development of Merten's " Haus " is there satisfactorily explained, a
phenomenon I have not yet witnessed; but in none of the
examples examined does the author report the occurrence of
the conditions encountered by myself.
In conclusion, it is not without the greatest diffidence I
venture to record the result of my own observations, after the
diversely expressed opinions of naturalists of such high
standing; yet I the more willingly do so, in the hope that
it may lead to further investigation, and still more important
discoveries on the part of those to whom these ocean waifs
are already to a large extent familiar.
Larva O/ECHINORHYNCHUS ? (PI. XIV, figs. 5—7.)
Remarks on this form will be published in a future number
of this Journal. The examples from which the accompanying
drawings were made were taken floating at the surface of the
sea, on the same day and under similar circumstances to
those associated with the capture of the Appendiculariae.
An IMPROVED APPARATUS for
SCOPE.
DRAWING with the MICRO-
By E. T. NEWTON,- H.M. Geological Survey.
T H E camera lucida, which, is very generally used for
drawing with the microscope, has, in common with most of
the instruments used for this purpose, the disadvantage of
requiring the microscope body to be placed in a horizontal
position.
The inconvenience of having to move the microscope after
the object has been adjusted, makes it very desirable that
some means should be devised by which this could be obviated. The instruments described by M. Nachet, jun.
{' Quart. Micros. Journ.,' Vol. V I I I , p. 158) all require the
microscope to be placed in a definite position, and are somewhat complicated. As these are constructed upon a principle
altogether different from that of the apparatus under consideration, it will not be necessary here to do more than call
attention to them. A form of prism described by Dr. John
Antony, as Nachet's, 1 when mounted in the same way as a
camera lucida, can be used for drawing when the microscope
1 ' The English Mechanic/ Dec. 2, 1870, p. 251.
271
is set at a certain angle. It is not, however, always convenient to use the microscope at one definite inclination, and
for this reason I think that the instrument about to be
described will commend itself, since it can be used with the
greatest ease whatever may be the angle at which the
microscope is inclined. It has also the advantage of being
simple in construction, and consequently inexpensive.
This apparatus is, as will be seen, a modification of the
steel disc of Soemmering,1 and the neutral tint reflector
described by Dr. Lionel S. Beale.2 It consists essentially of a reflector, which, can he inclined at any angle;
and when set for drawing, is used in exactly the same way
as the camera lucida. The arrangement will be best understood by reference to the accompanying figures:—(a) is a
silver or steel reflector, the upper edge of which is made thin
like a knife blade, as indicated in fig. 3, so that the view of
FIG.
IIG.
2.
1.
FIG.
3.
the pencil used in drawing may not be interfered with.
1
Vide Dr. Carpenter, ' The Microscope and its Revelations,' 4th edition,
p. 3100.
' How to Work with the Microscope,' 4th edition, 1868, p. 27.
272
This is most necessary when the microscope is being used at
a high angle. The reflector is supported upon the rod (b),
which turns, not too easily, in the socket (c), by means of
the milled head (d), so that the reflector (a) may be placed
at any angle desired, as shown by the dotted lines in fig. 3.
The socket (c) is firmly fixed to a second rod (e), which
turns somewhat tightly in the tube ( / ) . The ring (g) to
which the tube (/) is immovably attached serves to connect
the apparatus with the eye-piece of the microscope, which
may be done either before or after the object is arranged and
focussed. If placed in position before the object is arranged,
it can be turned on one side, so as to be out of the way, as
indicated by the dotted lines in fig. 2. When it is desired
to draw any object that is under the microscope, the reflector
is turned into the position shown in fig. n , until it receives,
close to its thin upper edge, the pencil of light from the eyepiece. The ring (g) is now turned upon the eye-piece, until
the upper edge of the reflector is exactly horizontal. By
means of the milled head (d) the reflector should now be set
at an angle with the drawing paper, this angle being just
half the magnitude of that formed by the axis of the microscope and the paper. When thus arranged, which is accomplished more rapidly than can be described, the instrument
is used in exactly the same manner as the camera lucida;
and any one familiar with the camera would find no difficulty
in its use.
For those persons who prefer drawing -with, the Beale
neutral tint reflector, an ordinary thin cover glass1 may be
substituted for the metallic mirror, and the apparatus arranged as before, except that the pencil of light from the
eye-piece need not fall upon the reflector close to its upper
edge, as the drawing pencil can be seen through the glass;
whilst in using the metallic reflector, the eye must look over
the thin edge in order to see the image of the object and the
pencil at the same time.
This apparatus may be used when the microscope is horizontal, or when nearly perpendicular, or at any angle between
these two positions. It has also this advantage over the
camera lucida, that the object which the microscope has
reversed, is again brought into its natural position.
1
There is no necessity for this to be tinted, as the light may be otherwise
moderated.