GERMINAL LOCALIZATION IN THE EGG OF CEREBRATULUS. 17 



A comparison with Series F (Fig. 10) will at once reveal 

 that the localization of the enteron stuff has not greatly advanced 

 during the period extending between the beginning of the first 

 cleavage and its completion. 



Series L. Cutting Experiment near the End 

 of the Second Cleavage. 



When the second cleavage was n«ar completion two blas- 

 tomeres were cut apart in two different ways ; (a) along the first 



cleavage plane and (b) 

 along the second. By 

 doing this two different 

 sets of fragments were 

 obtained as is seen in the 

 diagrams (Fig. 15). On 

 comparing the pilidia 

 developed from these two 

 different sets I was not 

 able to detect even the 



A, and B, diagrams showing two different 

 planes of section in series L. 



slightest difference between them. From this the conclusion may 

 be drawn that by this period the egg substances (excepting the 

 d4 element from à 2^riori grounds) are arranged uniaxially and 

 their bilateral differentiation comes in much later. 



Series M. Eemoval Experiment performed at the 5-cell Stage. 



A portion of cytoplasm was cut off from two eggs at the 

 4-cell stage as indicated in the right hand figure and both yielded 

 perfect pilidia. Another egg was cut as in the left hand diagram 



