CYTOLOGICAL STUDIES OF CEXTRIFUGED EGGS 
611 
The interest in the experiment is twofold; it shows to what extent 
the yolk, oil and pigment are distributed to each cell in develop- 
ment, and it shows, or might show, how soon these substances are 
used up in the respective cells or whether they are added to during 
development. In Cumingia it is evident that all the early cells 
get yolk, oil, and pigment, the relative amount being in propor- 
tion to the size of the cells. The distribution of the pigment and 
yolk, plate 2, fig. M, is such as to lead directly to such a result, 
provided they are not segregated during development, which 
does not appear to be the case from the evidence here furnished. 
The oil cannot be readily identified in the normal egg, but obvi- 
ously it, too, must be equally diffused in the egg. There is no 
evidence that any of these substances increase during the early 
cleavages, or that they are used up, at least in amounts that could 
be detected. 
The evidence shows, therefore, that while these three visible 
substances, yolk, oil, pigment, are present in all the early blasto- 
meres, their absence from these cells does not prevent normal 
cleavage or development and their presence in excess does not 
interfere with the normal j^rocess. 
Centrifuging eggs in the ovary 
In the vain hope that the chromosomes might be moved at the 
time when the large germinal vesicle breaks down, I tried to 
obtain eggs in this condition. The Cumingias were put into dishes 
of water and just before the expected time of oviposition, or just 
after the first eggs were set free, the animals were opened, the ovary 
taken out and the pieces centrifuged at once in the tubes. In 
most cases the germinal vesicle had disappeared, even while the 
eggs were still in the ovary ; or had not broken down at all. In 
only two or three cases did I obtain eggs in an intermediate con- 
dition. In none of these were there evidences of the indepen- 
dent movement of the chromosomes. The spindle that is already 
present in many of the eggs, although feebly developed, was in 
connection with the chromosomes, plate 4, fig. 4. 
