308 Maine Agricultural Experiment Station. 1917. 



SEX STUDIES. IX. 



Interstitial Cells in the Reproductive Organs of the 



Chicken.* 



True, secreting, interstitial cells appear to be always present 

 in the ovary. These cells are strictly homologous, and indeed 

 cytologically identical in the fowl and in the cow. Further- 

 more these cells are cytologically identical in the male, when 

 they are present, and in the female. 



In the fowl true interstitial cells are sometimes present 

 in the testis at the time of hatching. We have found no trace 

 of them in the testes of a large series of adult males. 



In general, the facts as to the occurrence and distribution 

 of interstitial cells are such in the fowl as to make it very dif- 

 ficult to suppose that these cells have any casual influence upon 

 secondary sexual characters. 



STUDIES ON INBREEDING. VIII. 

 A Single Numerical Measure of the Total Amount of 



iNBREEDING.f 



The need has been felt for a single numerical measure of 

 inbreeding to supplement or replace the inbreeding curves. 

 Such a constant has been found, which, it is believed, uniquely 

 and rigorously meets the requirements. This new constant is 

 defined by 



Tn ^ „ 

 100 FTn 



*This paper is an abstract from a paper by Alice M. Boring and 

 Raymond Pearl, having the same title and published in the Anatomical 

 Record, Vol. 13, No. 5, pp. 253-268. 



fThis paper is an abstract from a paper by Raymond Pearl, having 

 the same title and published in The American Naturalist, Vol. LI, No. 

 610, pp. 636-639. 



