DESCRIPTION OF THE SEXUAL PRODUCTS. 



21 



Why are the male sexual cells so small and thread-like, and so 



ilitierently constituted from the eggs ? 



The dissimilarity between the male and the female sexual cells is 

 explained by the fact that a division of labor has arisen between the 

 two, inasmuch as they have adapted themselves to different missions. 



Fig. 10 A and B. Initial stages of the metamorphosis 

 of the seminal cell into the seminal filament, 



after Hi: KM \\v 



A. Seminal cell with peai '-.-haped nucleus; />'. seminal 

 cell with cone -shaped nucleus ; sc, seminal eell ; , 

 nucleus witli chromatin network, and nnrleoli (); 

 mst, boil} out of which the middle piece is de\ eloped ; 

 r, vin:4-like structure, which is in contact \\itli the 

 middle piece, and is claimed to have relation to the 

 formation of the spiral membrane of the filament ; 

 t\ caudal appendage of the seminal filament. 



Fig. 11 A and B. Two terminal 

 stages in the metamorphosis 

 of the seminal cell into 

 the seminal filament, after 

 FLEMMINO. 



k, Nucleus, which has become 

 elongated to form the head 

 of the spermatozoon; mat, 

 its middle piece ; /, its 

 caudal filament. 



The female cell lias assumed the function of supplying the substances 

 whu-h are necessary for that nutrition and growth of the cell proto- 

 pla.Mn \\hieh a rapid accomplishment of the process of development 

 demands. It has therefore, while in the ovary, stored up in itself 

 yolk-substance, reserve material, for the future; and consequently 

 has Income large and incapable of motion. But inasmuch as it 

 is necessary for the accomplishment of a process of development 

 that union with a second cell from another individual should take 



f" ice, and since non-motile bodies cannot unite, theiefore the male 

 n;enf has Iveu suitably modified to meet this second requirement. 



