SEXUAL AND ASEXUAL REPRODUCTION 255 



Figure 122 // to ///. In this case, however, the division does 

 not produce one large and three small cells, but four cells of 

 equal size, each one of which receives two of the chromosomes. 

 It is evident, therefore, that one of these cells is equivalent to 



FIG. 122. DIAGRAM SHOWING A COMPARISON BETWEEN THE MATURA- 

 TION OF AN EGG, B, AND THE FORMATION OF THE SPERMS, A 

 Stages / to IV in series A and B correspond with each other. 



one of the cells developing in the maturation of the egg, at 

 least so far as concerns its nuclear matter and its chromosomes, 

 differing, however, in the amount of cell substance that may 

 be present. In the further development we find another point 

 of difference in the fact that each one of these four cells de- 

 velops into a perfect, functional sperm. In the maturation of 

 the egg, three out of the four cells are thrown away and take 

 no further part in the functions of the animal; in the develop- 

 ment of the sperm, however, each one of the four cells arising 

 from the divided spermatocyte cell becomes a typical sperm; 

 Fig. IV. It is evident from this that a sperm must be regarded, 

 so far as concerns its nuclear matter, as equivalent to a matured 

 egg, and equivalent also to each of the three discarded cells 

 which have been thrown away in the maturation of the egg. 

 Both the sperm and the egg contain half the normal number 

 of chromosomes. 



An examination of a matured sperm shows the structure 

 -'ndicated in Figure 121 sp. It consists of a head, which is 



