ROBERT CHAMBERS 



59 



centers was not disturbed. Each of the two pieces resulting from 

 the cut, therefore, consisted of two unequal semisolid masses sepa- 

 rated by a fluid area corresponding to the equator of the original egg. 

 As this fluid area is incorporated into the two masses a furrow appears 



Fig. 7. Effect of cutting off a piece from one pole of an Arbacia ovum in the 

 amphiaster stage, a, direction of cut. b, the piece cut off cytolized. The 

 original shape of the remainder of the egg persisted for some time as the ovum of 

 Arbacia is less pliable than that of Asterias. c, the reappearance of a new 

 amphiaster resulting in the formation of two equal blastomeres. 



which separates each piece into a larger nucleated and a smaller non- 

 nucleated body. 



The operated eggs were kept under observation until the gastrula 

 stage, indicating that the operation had not destroyed the capacity 

 of the egg for further development. 



