638 
T. H. MORGAN 
at issue concerning the so-called formative stuffs. There is one 
matter, however, of special importance. It may be claimed, and 
has, in fact, been intimated, that a redistribution of the cen- 
trifuged materials may take place so that the first separation 
is not present later. In fact mixing does occur, due in part to the 
entrance of the sperm, but primarily to the movements instituted 
by the karyokinetic division. But if the eggs are centrifuged 
during the division this remixing can be counteracted, and in any 
case its importance has been exaggerated. At least, I find little 
or no evidence that the different materials return to their former 
positions in the short time elapsing before cleavage. In unfer- 
tilized eggs the distinctions are as great, if not quite so sharp after 
24 or 48 hours as they are at first. 
In order to meet, as far as possible, criticism of this kind, I 
have made some experiments with the eggs of Hydatina. Im- 
mense numbers of individuals were collected at the surface of 
the culture by the method that Whitney worked out. These were 
put into shallow watch crystals, and poured off after five minutes 
or less. A few eggs are generally laid during this time. These 
were centrifuged at different intervals after laying. The time of 
the first cleavage, and its location in relation to the ''stuffs," 
was noted; and this record gave a further control on the condi- 
tions of the egg when centrifuged. 
The results may be stated in a few words. Normal embryos 
were obtained irrespective of the time when the centrifuging took 
place. In some instances division followed almost at once on 
removal from the machine and normal embryos resulted. There 
could have been no question of a redistribution of materials in 
such cases. At first the eggs were put into spring water. Here 
the}^ developed and often hatched, but the individuals, although, 
sometimes normal in structure, appeared still and dead. Such 
evidence might readily have led to the conclusion that the cen- 
trifuging was the cause of this premature death. Such a con- 
clusion would have been entirely wrong and shows how careful 
one should be in drawing conclusions concerning the injurious 
effects of the separation of the materials by the centrifuge. Cum- 
ingia taught the same lesson from another standpoint. I found 
