THE LAW OF BIOGENESIS 79 



tory process. The nucleus is the center of these 

 preparatory changes which have for their main 



purpose the elimination of a large amount of chro- 

 matin. In accomplishing the elimination of this 

 chromatin, some of the actual chromosomes are 



Figure 25. Diagram to show in outline sonne of the changes 

 that sperm cells pass through in changing from a typical cell 

 into the mature sperm. In this process each sperm-mother cell 

 gives rise to four mature sperms, each of which is capable of 

 fertilizing the egg. As the growth changes take place, there 

 is a sorting and reduction of the chromosomes so that each 

 sperm has but one-half as many as the sperm-mother cell. It 

 has also been shown by recent studies that the sperms are not 

 the same in the nature of their chromosomes. 



cast out of the egg. The result is that the egg 

 comes to have a nucleus that has but one-half as 

 much chromatin and one-half as many chromo- 

 somes. The diagram in Fig. 24 indicates how 



