82 JOSE F. NONIDEZ 



endocrine function. This view is strengthened by the fact that 

 the plumage, which in the cock is one of the most marked sec- 

 ondary sexual characters, changes but very slightly after castra- 

 tion. The observers who accept the existence of an interstitial 

 endocrine gland have described cells which show granules stained 

 after certain specific treatments, regarding such granules as the 

 secretion of the cells. But in a few instances the mere presence 

 of cells differing morphologically from the ordinary connective- 

 tissue cells has been regarded as a decisive proof of the existence 

 of an interstitial gland. 



While the morphological side of the question has been repeat- 

 edly attacked in the adult cock, no careful observations have 

 been made on the histogenesis of the testis, especially on the 

 processes of differentiation taking place in the tissues lying 

 between the seminal tubules. As in most organs in the body, the 

 testis is a complex structure made up of different tissues. Aside 

 from the seminal epithelium forming the tubules, 'there are blood- 

 vessels, lymphadenoid nodules, and connective tissue. The last 

 exhibits a remarkable complexitj^ on account of the presence of 

 wandering cells produced as a result of its hematopoietic capacity 

 which, though more conspicuous during development, does not 

 cease altogether in the adult bird. It is extremely difficult, 

 therefore, to decide on the nature of certain cells present in the 

 gonads unless the histogenesis of these organs has been carefully 

 followed and their connective tissue compared with that found 

 in other regions of the body, both in the embryo and in the adult. 



The existence of a distinct interstitial tissue in the ovary of the 

 hen has been reported by Sonnenbrodt, Ganfini, Poll, and Firket. 

 It consists of cells with polygonal outline and round nucleus sur- 

 rounded by a highly vacuolated cytoplasm (fig. 1, ?i). These cells 

 usually appear in the form of clusters in the medullary portion 

 of the gonad and around the follicles. The aspect of the tissue 

 strongly points to its epithelial origin. As shown by Firket ('14), 

 such cells arise as a differentiation in the epithelial elements which 

 form the sexual cords of the first proliferation, the germ cells 

 degenerating in the meantime. ^ 



2 A detailed account of the origin of this interstitial tissue in the ovary will be 

 given in another paper dealing with the histogenesis of the gonads. 



