34 THE GENETIC AND THE OPERATIVE EVIDENCE 



to Mann's and Mallory's methods. In addition, a whole new series 

 of preparations was made. A few interstitial cells, i. e., granule con- 

 taining-cells were found in newly hatched chicks, but not in any of 

 the 60 mature birds examined. 



LUTEAL-CELLS IN THE TESTES OF THE MALE SEBRIGHT. 



Finding that the testes of F 2 hen-feathered birds were often flat and 

 pear-shaped instead of rounded and cylindrical, as in ordinary cocks, 

 and that they were often black in color, suggested, as already stated, 

 that the testes of the Sebright might be hermaphrodite in some element. 

 It seemed not impossible that egg-cells might be found. I made a 

 considerable number of sections of the testes of these birds and 

 examined them under the microscope; not finding any egg or egg-like 

 bodies, the slides were laid aside, but the idea that in some other way 

 the Sebright's testes might correspond to the ovary of the female next 

 recurred to my mind. Consequently, when in the summer of 1918 I 

 had some new material derived from a castrated Sebright male that 

 had partly regenerated its testes and was again going back to hen- 

 feathering, and pieces from one of the old testes of a castrated bird, 

 I asked Miss Boring, who was then in Woods Hole, to make some 

 preparations and examine them to see if she could detect any such 

 elements in them as she had found in the female. Miss Boring 

 reported the occurrence of luteal cells in the testes from hen-feathered 

 males, and the results have been published in a brief preliminary paper 

 (1918). The abundance of these clear cells, supposedly gland-cells 

 with endocrine influences, in the testes of hen-feathered birds is in 

 sharp contrast to their absence in the normal adult cock birds. It 

 seems to follow, therefore, that the hen-feathering in the Sebrights is 

 due to the presence of these cells, whose function is the same as of the 

 similar cells in the female, i. e., the suppression in both of cock-feather- 

 ing. Castrating the Sebright produces its effect by the removal of 

 these cells that are responsible for the suppression of cock-feathering. 



The occurrence of luteal cells in young stages of other races of poultry 

 raises the question as to whether in these races the first or juvenile 

 plumage, that resembles that of the hen rather than that of the cock, 

 may not also be due to an internal secretion from these cells, or whether 

 this juvenile plumage is only the plumage of a characteristic stage in 

 development. Castration of young chicks ought to settle this point. 

 Such castration experiments have been made by Goodale. The 

 absence of any reference to any effect on the juvenile plumage in 

 these early castrated birds probably meant that they did not develop 

 precociously cock-feathering, and he writes me that he examined them 

 carefully and that their plumage is like that of the normal chicks. 

 Geoffrey Smith has reported the occurrence of two kinds of males 



