654 THE PHYSIOLOGY OF REPRODUCTION 



opposite sex. In this connection it is important to note that 

 the removal of the testes in the male is believed in certain 

 instances to lead to the development of the secondary female 

 characters, and that conversely the extirpation of the ovaries 

 in the female is said sometimes to cause the assumption of the 

 male characters (see p. 314). Moreover, Darwin and others have 

 shown that female birds (e.g. poultry, pheasants, ducks) in old 

 age, when the ovaries are no longer functional, or in cases where 

 these organs are diseased or have been injured by shot, some- 

 times acquire the secondary sexual characters of the male. So 

 also Wallace l states that aged mares tend to assume the arched 

 neck characteristic of the stallion. Conversely, cases are re- 

 corded in which characters and habits ordinarily confined to the 

 female are assumed by the castrated male. Thus Darwin states 

 that capons have been known to incubate eggs and bring up 

 chickens, and that sterile male hybrids between the pheasant 

 and the fowl may act in a similar manner. Such cases as 

 these are evidence of the latency of characters belonging to the 

 recessive sex in individuals of the other sex. Furthermore, 

 in studying the sexual pathology of youth and old age, there 

 are a number of well-ascertained facts that point in a similar 

 direction. 



Weininger 2 has elaborated the idea that just as there may 

 be an " Idioplasm " that is the bearer of the specific characters 

 and exists in all the cells of a multicellular animal, so also 

 there may be two sexual modes in which this idioplasm can 

 appear, namely an " Arrhenoplasm " or male plasm, and a 

 " Thelyplasm " or female plasm. He maintains further that 

 every metazoon cell (and not merely every reproductive cell) 

 has a sexuality lying somewhere between arrhenoplasm and 

 thelyplasm, but that the actual degree of maleness or femaleness 

 varies in the different groups of cells of which the animal is 

 built up. Moreover, the different parts of the organism are 

 supposed to possess their own sexual determinants, which are 

 believed to be stable from their earliest embryonic foundation. 

 Weininger makes no suggestion as to what it is that determines 



1 Wallace, Farm Live-Stock of Great Britain, 4th Edition, Edinburgh 

 1907. 



2 Weininger, Sex and Character, English Translation, London, 1906. 



