78 W. W. SWINGLE. 



spindle fibres; actual division of the body was observed but 

 once. (See Fig. 29.) The body is readily distinguished from the 

 chromosomes by its peculiar character, and the position it takes 

 during cell division. 



In the primary spermatocytes the chromatoid body is con- 

 spicuous in the cytoplasm. Whether it does or does not divide 

 at the first maturation division was not ascertained. In Fig. 

 24 it is shown passing to one pole, apparently undivided. 



I make mention of the behavior of this structure here, in order 

 to disarm, beforehand, the criticism which perchance might 

 arise in connection with this paper, that I may have mistaken 

 the chromatoid body for an accessory chromosome. The origin 

 and fate of this peculiar body in Rana pipiens seem worthy of 

 further investigation. 



SUMMARY AND CONCLUSION. 



1. The oogonial number of chromosomes in Rana pipiens and 

 catesbiana appears to be twenty-six. 



2. The spermatogonial number is twenty-five in Rana pipiens. 



3. In the synaptene stage of the germ, cells of the female 

 Rana pipiens larvae, a chromatin body is found which simulates 

 the behavior of an accessory chromosome. 



4. The reduced number of chromosomes in the male of Rana 

 pipiens is thirteen. 



5. At the first maturation division of the germ cells of a frog 

 possessing marked hermaphroditic tendencies, there is an unequal 

 distribution of chromatin to the daughter cells, the inequality 

 varying in different cells. 



6. Perhaps this unequal distribution of chromosomes at the 

 spermatocyte division and the resulting inequality of chromo- 

 somal distribution to the spermatozoa may account for the fact 

 that males, females, and animals possessing marked hermaph- 

 roditic tendencies are found in this species of frog. 



In conclusion, I wish to acknowledge my indebtedness to 

 Dr. B. M. Allen for the loan of several valuable slides and to 

 Dr. W. R. B. Robertson for several excellent suggestions. 



April ii, 1917. 



