co The effect of the Parasites ori their hosts. 



of sex and of hermaphroditism can be of universal application. The most serions objection 

 to this view is that in certain rare cases, chiefly among fowl and deer — see Herbst (16) and 

 Rorig (17) — individuala which have actually functioned as females and which show no trace 

 of male gonads may subsequently acquire the secondary sexual characters of the male sex, 

 and these cases, at any rate in the case of deer, merge into those where a female with diseased 

 or at least non-functional gonads may acquire secondary male characters. Although these 

 cases are strong prima facie evidence in favour of the view that the female sex may normally 

 carry the male in a latent condition, their rarity and the fact that they merge so completely 

 into ordinary cases of hermaphroditism, may make us suspect that these apparently once 

 normal females have been from the beginning hermaphrodites in which for some reason the 

 male sexual formative substance did not find expression in visible characters. Another body 

 of facts may seem fatai to our view, the facts showing that the male characters can be 

 transmitted through the female sex, as in the case of hybrids and of parthenogenetic females 

 which give rise to males. But a legitimate distinction can be drawn between the presence 

 of a metabolic substance in the body capable of assuming activity under the proper stimuli, 

 and the transmission of a sexual potentiality which may depend on some quiescent structural 

 element incapable of activity except after the elaborate and mysterious changes which accom- 

 pany the inception of a new generation. 



The theory that the male sex alone normally carries the formative substance of the 

 opposite sex receives a certain value if we apply it to those classes of animals descended 

 from dioecious ancestors which have become secondarily hermaphrodite. In view of a number 

 of considerations which are urged at the end of Chapter 6, it is difficult to maintain that 

 hermaphroditism, as an apparently necessary concomitant to a fixed habit of life, can be 

 accounted for as a mere adaptation for securing reproduction. In this chapter we have 

 seen how a complete state of hermaphroditism can be imposed upon certain individuals of 

 the male sex, as the result of a degenerate process initiated by the presence of a parasite, 

 which apparently works through an affec tionof the general conditions of metabolism. In 

 ordinary fixed hermaphrodite animals we meet with undoubtedly a peculiar condition of 

 metabolism, and a general process of degeneration which usually affects the whole organization. 

 It is, therefore, reasonable to suppose that the hermaphrodite state in fixed animals has been 

 acquired by simple degeneration, imposed upon the male organism as an adaptive response to 

 the changed conditions of metabolism incident on the fixed habit of life. 



If we argue that secondarily acquired hermaphroditism is always a form of degeneration, 

 or the passage from a higher to a less degree of metabolic specialization, it is more probable 

 that this state has been imposed upon the male sex than upon the female, because the former 

 is the more highly organized of the two, and for the female to acquire male characters, 

 i. e. to become hermaphrodite, would mean an advance in organization and not a retrogression. 



We arrive therefore at the unexpected, but not impossible view that animals which 

 have become hermaphrodite through a fixed method of life, are represented merely by the 



