Nucleoli
and
SAT-chromosomes
401
SATO (l937) holds that prophase is the best stage in
AloJnae for observing satellites. T o the writer the ana­
phase seems to be the best stage in order to secure the
best observations of the SAT-constrictions. Henceforth
we can assume that the metapbase is an unsuitable stage
for the observation of these structures, although it was
for GEITLER (l936) the only stage for observing clearly tbe
SAT-constrictions of Rhizoclonium
IV. A s regards the
other phases he s a y s : «Die Trabanten sind unter beson­
ders günstigen Umständen auch in der Anaphase sichtbar;
dagegen ist es mir nicht gelungen, sie in der frühen P r o ­
phase oder im Ruhehern nachzuweisen», LEVAN (l936)
observed satellites very easily in the division of gamophase of Allium Schoenoprasum, whereas in zigophase they
can scarcely be noticed.
It must be recommended that the observation of satel­
lites (— SAT-constrictions) must be extended to all the
phases, so as to cover the most favourable stages, as the
latter vary from plant to plant. Moreover it is necessary to
recommend the use of suitable fixing and staining agents.
In many cases the satellites are very difficult to detect
because they are either too small, thus escaping notice
(cf. RESENDE 1936 a and 1937 a, SATÖ 19376 and KUHN 1938),
or they are hidden by the other chromosomes of the chromosomic set or by the satellite-chromosome itself. Also
the connection between the chromosome and the satellite
may be responsible in certain phases, or in all, for the
difficulty of its observation, even microscopically impos­
sible sometimes. Sometimes the absolutly clear mitosis sui­
table for the numbering of the chromosomes are unfit for
the ascertainement of satellites on account of the disposi­
tion of the chromosomes each to other.
These studies must stand on sound bases, as careless
observations often lead to statements on the non-existence
of satellites, which further observations of the same ma­
terial by another worker prove to be incorrect (cf. RESENDE
1936 a, 1937 a).
* *
A s regards the observations of DOUTRELIGNE one must