GEKMINAL LOCALIZATION IN THE EGG OF CEREBRATÜLUS. 15 



Forty pilidia resulted from tliis operation ; of tliese nine 

 were slightly defective and the rest were perfect. The apical 

 organ has a tendency to shift to one side as has just been 

 mentioned in the case of Series G. The double apical organ is 

 not infrequent. The enteron is usually straight, especially in 

 the young pilidia. The slight abnormality noticed by Wilson 

 ('03 p. 432) may sometimes occur, yet in general one would not 

 hesitate to call the resulting larvae normal. And the development 

 is considerably retarded in the case as has been noticed by 

 Zeleny ('04 p. 313). 



Series I. Isolation and Removal Experiment at the 2-cöll Stage. 



The blastomeres, which were isolated 

 from their fellows at the 2-cell stage, were 

 cut along various planes, such as a, b, c, 

 and d indicated in the diagram (Fig. 12). 

 Fourteen pilidia were obtained. Owing to 

 the paucity of cases it will not be safe to 

 draw any conclusion. However, it might 

 be well to state that the cuts c and d, and 

 horizontal ones are liable to cause anen- 



teria ; the cuts a and b hardly modify the embryogénie processes 



at all. 



Fig. 12. 



Diagram showing cut- 

 ting planes in Series I. 



Series J. Removal Experiment at the 2-cell Stage 

 Performed on One of the Blastomeres. 



One of the blastomeres of the 2-cell stage was cut along three 

 different planes (Fig. 13). Twenty-nine pilidia were obtained. 



