2Q2 J. E. WODSEDALEK. 



larger owing to the presence of a large sex-chromosome or acces- 

 sory element which is lacking in the type producing maleness. 

 Since it has been found in this study that the oogonia of cattle 

 possess two sex-chromosomes it is safe to conclude, in view of 

 our knowledge of oogenesis in general, that all of the mature ova 

 carry the reduced number or one sex-chromosome. If the ovum 

 is fertilized by a sperm which lacks the sex-chromosome the 

 resulting zygote naturally possess only one sex-chromosome and, 

 therefore,. develops into a male. This is evidenced by the fact 

 that the somatic as well as the germ cells of the male possess 

 a single accessory element. On the other hand, if the ovum is 

 fertilized by a sperm possessing the sex-chromosome the resulting 

 zygote possesses two sex-chromosomes and, therefore, develops 

 into a female. The somatic as well as the germ cells of the female 

 possess the two accessory elements which is in exact accord with 

 expectations. 



The results presented in this paper were obtained through a 

 most careful and critical study extending over a period of more 

 than four years. The problem was started in the spring of 1915 

 and every summer since and a great deal of the spare time in the 

 intervening school years, with the exception of the year 1918, has 

 been devoted to it. In the aggregate this means a total of about 

 fifteen months of continuous work. Practically all of the results 

 presented in this paper were at hand at the end of the first two 

 and a half years of study. Over four hundred pencil sketches 

 were made of the various cells, especially those in mitosis, with 

 the aid of the camera lucida and the location of each, as indicated 

 by the mechanical stage, was carefully recorded in a separate 

 booklet. A brief summary of the results of the study was 

 written up and all of the material was put away for a whole year 

 (1918) during which the summer months and other spare time 

 was devoted to the study of the sex cells in another mammal. 

 No effort was made to remember any of the results of the study 

 on the sex cells in cattle. 



In the meantime, considerable new cattle material was obtained 

 and hundreds of new slides were made by the departmental 

 technician. At the end of the year the new cattle material was 

 studied and the results were carefully recorded. The original 



