No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
323 
present ; from these differences in form he concludes that the 
nucleolus may be capable of amoeboid movements. Subse¬ 
quently it wanders towards the center of the nucleus, becomes 
larger and more spherical. When the chromatin has assumed 
the characteristic radial distribution, before the first maturation 
division, the nucleolus passes again towards the periphery, and 
there becomes gradually smaller, partly by fragmentation, and 
so gradually disappears. 
Holl (’90) found one spherical nucleolus in ova of the newly 
hatched chick: “ Da das Kernkorperchen so auffallend verschie- 
den vom Kernnetze und Kernsafte hinsichtlich des Verhaltens 
zur Farbe sich zeigt, so muss es wohl aus einem anderen Stoffe 
bestehen als jene. Auch bei Salamandra y Rana , und Lacerta 
fand ich das Kernkorperchen immer sich verschieden halten 
von den anderen Theilen des Kernes.” The nucleolus is always 
situated excentrically at the upper pole of the nucleus. Towards 
the end of the spirem stage the nucleolus lies on the periphery 
of the chromatin, with which it stands in no close connection; 
it is no longer present in ova of 491 / 1 , diameter. 
Kastschenko (’ 90 ) investigated the maturation of the ova of 
Pristiurus , Scyllium, and Torpedo: there are numerous nucleoli, 
which attain a diameter of 1 6 /x, and all disappear at the 
spirem stage (in the prophase of the first pole spindle). Each 
nucleolus contains a large unstaining globule (but in his Fig. 1 , 
in several of the nucleoli, all of which had been stained with 
borax carmine, this globule is colored blue, while the peripheral 
portion of the nucleoli is red). 
Masius (’ 90 ): in the ovum of Asplanchna the nucleolus forms 
the greater part of the nucleus. In Lacimdaria it is at first as 
in the preceding genus, but at a later stage several much smaller 
nucleoli are found. 
Mellissinos and Nicolaides (’90), pancreas cells of Canis: The 
“Nebenkern ” is a plasmosome which has wandered out of the 
nucleus; this migration is caused by an injection of pilocarpin 
into the living gland. 
Sheldon (’ 90 ) found one germinal spot in Peripatus capensis, 
which disappears when the nucleus reaches the periphery of 
the egg. 
