THE ACCESSORY CHROMOSOME IN A FROG POSSESS- 

 ING MARKED HERMAPHRODITIC TENDENCIES. 



W. W. SWINGLE, 

 DEPARTMENT OF ZOOLOGY, UNIVERSITY OF KANSAS. 



INTRODUCTION. 



In the spring of 1916, the writer, while engaged in determining 

 the effects of starvation upon the development of the germ cells 

 and germ glands of larval frogs, noticed an odd chromosomal 

 body in the germ cells of Rana pipiens, which simulated the 

 behavior of an accessory chromosome. Owing to the pressure 

 of other work at that time, the matter was neglected until early 

 in the fall of 1916, when a reexamination of my material led me 

 to believe that the body I had observed the previous spring was 

 probably an accessory or so-called "sex chromosome." 



The present paper is a brief preliminary statement of my 

 observations on the peculiar behavior of this body in the germ 

 cells of Rana pipiens. 



LITERATURE. 



So far as the writer is aware, there is little cytological evidence 

 of the presence of an accessory, or sex determining factor in the 

 germ cells of amphibia. Miss King in 1912 described dimorphism 

 in the spermatozoa of Necttirus maculosus resulting from unequal 

 chromosomal division. This brief paper seems to exhaust the 

 findings upon this particular subject. 



There is a great mass of literature dealing with cytological 

 studies of the germ cells of Urodeles, but with the exception of 

 Miss King's paper, inequalities in the distribution of chromatin 

 have never been reported. 



King, '07, failed to find any indications of accessory chromo- 

 somes in the germ cells of Bufo. So far as I am aware, -no one 

 seems to have worked with Rana pipiens, though the material is 

 excellent in every respect. 



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