C. J. Bond 207 



sharp and perinarient ariTst of growth if they have already begun to 

 develop before the castration was performed. 



Such are the facts, as experimentally determined, but the nature 

 of the association, and the way in which the removal of the sex 

 gland influences the growth of the tissues, are not fully known. 



Recent observations suggest that it is not merely the absence of one 

 sex gland that brings about the development of the opposite secondary 

 sex characters, but that there must also be the starting into functional 

 activity of some hitherto dormant elements in the degenerating gland 

 or in some other situation in order to bring about the evolution of the 

 corresponding sex characters. 



In other words, as Shattock has suggested, the presence of male 

 sex gland elements is necessary for the development of secondary male 

 characteristics in every individual whether the female sex gland be 

 present or not. The essential point is the presence of a stimulating 

 factor rather than the absence of an inhibiting factor. There are some 

 facts w^hich support this view thus : 



(a) In an increasing number of cases in birds in which atrophy of 

 the ovary has been found in association with the development of 

 secondary male characters, careful microscopical examination of the 

 degenerating female gland reveals the presence of islands of male 

 elements showing active growth. 



PI. XIII, fig. 13 shows such male gland elements in the degenerating 

 ovary of a hen pheasant in which male plumage and well developed 

 spurs were both present. 



(b) It is known that the gradual destruction of the normal tissue 

 of both ovaries by a new^ growth in young women is more often associated 

 with the growth of hair on the face, alteration in the voice, and the 

 appearance of other secondary male characters than is even complete 

 bilateral oophorectomy, the explanation being that the gradual destruc- 

 tion of the Graaffian follicles and interstitial cells by disease acts like 

 parasitic castration and affords an opportunity for the growth and 

 functional development of dormant rudiments of male gland cells 

 present in the degenerating ovary, while in complete bilateral oopho- 

 rectomy these male elements are removed along with the female gland 

 and all possibility of their subsequent growth is thereby prevented. 

 The same seems to be true of birds also. Mr Cooper of Knaresborough 

 has kindly sent me the photo of a Blue Leghorn Pullet which developed 

 a well marked comb and other male characters (but no spurs) ; in this 

 case the ovary was destroyed by a large new growth, 



14—2 



