smallwood: maturation of haminea solitapja. 311 



tion is accomplished by each of these two divisions. Since the chromo- 

 somes of the germinative vesicle probably lose their individuality during 

 the formation of the first maturation spindle in the ovotestis, qualitative 

 reduction cannot be demonstrated in Haminea. 



Fertilization. The sperm head may penetrate the ovum at any point 

 of its surface. A middle piece could not be distinguished. The sperm 

 head is not accompanied by a sperm aster, nor is there any sphere-sub- 

 stance associated with the sperm head. 



Accessory asters appear in the anaphase of the second maturation ; 

 these are temporary and independent of the sperm head. 



Cleavafje. The chromatin in both male and female pronuclei passes 

 through an elaborate metamorphosis before the cleavage asters arise. 

 Of the two cleavage asters one is associated in origin with each pronucleus. 



The centrosome at tlje close of each cleavage becomes indistinguishable 

 from the microsomes in the cytoplasm, and it is therefore impossible to 

 affirm that it divides in preparation for the following cleavage. 



