MATURATION 



151 



COMPARISON OF TYPICAL OVUM AND SPERMATOZOON 

 Similarities: 



Nuclei contain the haploid number of chromosomes, the result of 



two similar meiotic divisions. 

 Chromosomes alike in form, size, and, with a few exceptions of 



special significance, in number. 

 Can function only after syngamy. 



Differences: 



SPERMATOZOON 



Little cytoplasm. 

 No deutoplasm. 



Actively motile. 



Centrosome present. 



One of four similar products 

 of the division of the sper- 

 matocyte, all of which are 

 functional. 



Usually completely formed and 

 matured in the gonad. 



OVUM 



Much cytoplasm. 



Nearly always contains deuto- 

 plasm, often very large amounts. 



Non-motile. 



Centrosome absent. 



The functional one of four dis- 

 similar products of the division 

 of the oocyte, the other three 

 of which are alike and not func- 

 tional. 



Usually formed but rarely com- 

 pletely matured in the gonad. 



above, we should indicate at this time that the process has 

 significance from at least two points of view. As a preliminary 

 we should note that two different processes are involved in 

 maturation; first, a reduction in the number of chromosomes, 

 second, a reduction in the amount of chromatin. The earlier 

 idea that maturation is merely a process by which the germ 

 cells are rid of a part of then* chromatin, and one-half of their 

 chromosomes, as a preparation for the restoring union of 

 chromatin and chromosomes during fertilization, is only one 

 and probably the least important aspect. Many cells other 

 than germ cells gain and lose large amounts of chromatin, and 

 without going through any such complex process as that out- 

 lined above. Frequently much more than half, sometimes 

 fully nine-tenths, of the chromatin is lost from the oocyte 

 nucleus during maturation, while during spermatogenesis com- 

 paratively little may be lost. And the mere numerical reduc- 



