96 JOSE F. NONIDEZ 



cytes because the former agree in all respects with the cells 

 called 'interstitial' by Boring and Pearl. A careful comparison 

 of the descriptions and figures published by these observers and 

 the granulocytoblasts present in the gonads has proved beyond 

 any doubt the identity of both kinds of elements. 



Therefore, the close similarity of the 'interstitial' cells in the 

 two sexes of the fowl is not surprising, since they originate from 

 the same stem cells by entirely similar processes. Their presence 

 in the testis of newly hatched chicks can be easily explained on 

 account of the persistence of the granulocytoblasts produced by 

 the mesenchyme during the late stages of development. The 

 same can be applied to the case of the female. 



WTiile most of the granulocytes have disappeared at the time 

 of hatching, this does not mean that the hematopoietic capacity 

 of the mesenchyme has entirely ceased. It is true that in some 

 cases it has considerably decreased, and even no signs of it can 

 be detected. But the occurrence in both sexes of myeloid meta- 

 plasis shows that under certain conditions the formation of granu- 

 lar leucocytes may start again showing the same features of the 

 granulopoiesis in the embryo. This accounts for the presence of 

 granulocytoblasts in the mature gonads. Since these elements 

 are the only kind of granule-laden cells present in the ovary and 

 testis and are connected with typical eosinophile granulocytes 

 by a closely graded series of stages, it is safe to assume that they 

 do not constitute a tissue endowed with a specific endocrine func- 

 tion. A further proof of this is found in the fact that the gran- 

 ule-laden cells are not restricted to the gonads, but occur else- 

 where in the general mesenchyme. At least, it cannot be proved 

 that the cells present in the gonads differ from those in other 

 organs in any constant and fundamental characteristic. 



The interstitial nature of the granule-laden cells described by 

 Boring and Pearl, therefore, is- not warranted by any fact other 

 than a superficial resemblance with elements regarded as glandu- 

 lar in the testis of mammals. 



