THE MORPHOLOGY OF FERTILIZATION 



69 



animals. In some cases, as in Ascaris, the quantity 

 of cytoplasm thus introduced is very considerable 

 (Fig. 6a); in other cases, as in Nereis (Fig. 3), none can 



x'" 



\ 



a o 



FIG. 10. Fertilization of a nematode (Ancyr acanthus cystidicola) 

 (after Mulsow) : In each figure the upper nucleus is the egg nucleus, the 

 lower the sperm nucleus. In both figures the egg nucleus contains six 

 chromosomes; in a the sperm nucleus contains five chromosomes, in 

 b six. The combination 6 + 5 in a gives the male number, eleven; the 

 combination 6+6 in b gives the female number, twelve. The two 

 classes of spermatozoa are hence regarded as male producing and female 

 producing respectively. 



he demonstrated to occur. It is generally believed 

 with good reason that the perforatorium and tail have 

 no further significance in fertilization after penetration 

 is once achieved; in any event they are not traceable 



