THE GONADS OF THE FOWL 83 



Boring and Pearl ('18) have described this tissue in the ovary 

 of normal and hermaphrodite birds, but deny its interstitial 

 nature. They regard the cells forming the clusters as playing 

 an important role in the formation of the corpus luteum. Hence 

 the term 'lutear cells' which they have used throughout their 

 papers. The interstitial tissue is represented, according to these 

 observers, by certain granule-laden elements which they have 

 called interstitial cells. These cells are roundish and possess a 

 small, deeply staining nucleus; their cytoplasm is loaded with 

 abundant granules which stain a reddish-purple after Mann's mix- 

 ture and Mallory's triple stain, taking also the iron hematoxylin. 

 The granule-laden cells may be scattered through the stroma of 

 the ovary, but occur chiefly near the periphery. 



The most important point in connection with the existence of 

 these granular interstitial cells is that their presence is not con- 

 stant and seems to be influenced by the age of the bird. They 

 appear always in the mature female, but they are absent in the 

 ovaries of newly hatched chicks. The reverse condition occurs 

 in the males : the granule-laden cells were not found in the testis 

 of any of the sixty mature birds studied by the observers me-n- 

 tioned above, but occurred in those of four newly hatched chicks, 

 usually forming groups in the connective tissue in which they lie 

 embedded. A comparison of the granule-laden cells of the testis 

 with those present in the ovary showed that aside from certain 

 minor differences in the size of the cell-body and granules, as 

 well as in the structure of the nucleus, both kinds of cells are 

 identical in the male (when present) and the female. 



Since the granule-laden cells are not always present in both 

 * sexes. Boring and Pearl reached the conclusion that ''character- 

 istic, true interstitial cells are neither a necessary nor a constant 

 element in the make up of the testis in the male of the domestic 

 fowl." From this statement they draw the conclusion that " the 

 facts regarding the occurrence and distribution of interstitial 

 cells are such as to make it very difficult to suppose that thej^ 

 have any causal influence upon the secondary sexual characters" 

 ('17, p. 265). 



