262 H. M. KIXGERY 



rapidly succeeding divisions the amount of the chromatin and 

 the number of the chromosomes in the mature germ cells is 

 reduced to half that found in the somatic cells. There have 

 arisen in the interpretation and explanation of these facts dif- 

 ferences of opinion, some of which will be taken up later in a 

 discussion of synizesis and synapsis. 



Of the two processes, spermatogenesis has received more 

 attention; it is completed in less time and in many forms a 

 i^ingle adult testis will show all the stages of development from 

 spermatogonium to spermatozoon. Oogenesis, on the other 

 hand, is extended over a long period; in mammals at least and 

 in many other forms as well, the process may start in the 

 young embryo and continue into adult life. The formation of 

 the deutoplasm — vitellogenesis — ^with the consequent enormous 

 growth in size of the egg-cell, further complicates this process. 

 J\iaterial for the study of the development of the male germ cells 

 is easier to obtain, then, and is more convenient to work with. 

 Xevertheless, oogenesis has not been neglected. 



In 1900 V. Winiwarter published his paper on oogenesis in 

 the rabbit and man, and in 1908 there appeared his monographic 

 work in collaboration with Sainmont on the organogenesis of 

 the ovary and oogenesis in the cat. These two studies have had 

 an important influence on the work since done along similar 

 lines. An instance which might be mentioned is that the termin- 

 ology, first proposed by von Winiwarter and later slightly modi- 

 fied by both authors, has been adopted by a large number of 

 those who have made a study of oogenesis and particularly, 

 perhaps, of spermatogenesis. 



\'on Winiwarter and Sainmont state that they found the cat 

 a more favorable form to work with than the rabbit because the 

 period of gestation is longer (sixty days instead of twenty-eight) ; 

 the development of the animal is slower and consequently that 

 of the ovary is more gradual, which made it easier to obtain the 

 various stages. On the other hand, it seemed to me that it 

 might be desirable to make a study of a form which had a short 

 sexual cycle, which could be readily obtained in large numbers, 

 and which could be easily bred. The white or albino mouse 



