CYTOLOGICAL STUDIES OF CENTRIFUGED EGGS 
619 
2. CENTRIFUGING THE EGG OF CEREBRATULUS 
The eggs of Cerebratulus are large and laden with yolk. They 
can be obtained at the proper season in large numbers. The matu- 
ration takes place in the course of one to two hours after removal 
affording a good opportunity for applying a centrifugal force dur- 
ing this entire period. Since these stages could not be advantage- 
ously studied in Cumingia Iw^as anxious to make use of a form like 
this, w^hose eggs mature after removal. In another respect also 
Cerebratulus differs from Cumingia. If strongl}^ centrifuged the 
eggs may be drawn out into bottle-shaped forms (plate 7, figs. 37, 
44) and the neck of the bottle even separated from the body (fig. 
36, 38). The effect of the change in shape on the karyokinetic 
figure offers certain points of interest. 
Through the courtesy of Professor W. R. Coe of Yale University 
I obtained in his laboratory an abundance of material during 
March, 1908. At the Harpswell Laboratory I obtained further 
material during the summer of 1909. The combined results are 
here given. 
The enormous germinal vesicle lies slightly eccentric. Between 
it and the pole of the egg the cytoplasm contains less yolk and 
through this part the polar spindle reaches the surface. The 
cytoplasm is filled with large yolk granules and these are more 
abundant towards the antipole. When the eg^g is centrifuged, 
slowly a strange effect is sometimes produced as shown in plate 2, 
figs. W, X. A ring of yolk granules lies below the nucleus. Its 
interior is filled with a less stainable material with yolk granules 
scattered in it. Outside of the ring a purplish zone is found whose 
color is due to the mixture of yellow yolk and blue cytoplasm. 
If the egg is rotated for a longer time, the ring becomes solid, and 
finally the resulting ball of yolk is thrown down to the bottom of 
the egg (plate 7, fig. 37). On that surface of the ball that is 
turned towards the nucleus a zone of black-staining, finely granu- 
lar substance can be distinguished, and these granules are also 
found throughout the ring especially on its outer and inner sur- 
face, (plate 2, fig. X). 
The rest of the egg is filled with cytoplasm having a granular 
