INTERSEXUALITY 409 



conception of an hormonic intersexuality. There are individuals 

 which have the external characters of one sex on the right side 

 of the body and of the other sex on the left side ; this is not un- 

 common in insects, and has been observed also in other species. 

 In insects there is a very great variability in regard to this 

 "lateral" intersexuality. In some cases the internal sexual 

 organs correspond to those of the external; in others there is 

 no such parallelism, internal female sexual organs, for instance, 

 being present on the side of external male characters. There 

 are also cases where the internal organs are only of one sex, 

 whereas externally a marked unilateral intersexuality is 

 present. Meisenheimer's paper (1909, Chapter V.) may be 

 referred to. Examples have been described in moths, ants, 

 bees, Crustacea and other Arthropoda. In ants the variability 

 is particularly great. Here the external male and female sex 

 characters differ from one another very markedly in colour 

 and structure; as Forel (1874, pp. 139-143) points out, it is 

 possible to state with certainty to which sex every segment or 

 even every part of a segment appertains. I could assure 

 myself of this in examining Forel's beautiful collection. Such 

 a lateral intersexuality has been observed also in mammals 

 and in birds, in which, however, these cases are extremely rare. 

 In birds examples have been recorded by Poll, Weber, and Bond 

 (quoted from Doncaster, 1914). Poll's bullfinch had the male 

 and female plumage sharply separated on the two sides of the 

 body, the right side being male, the left side female. A testis 

 and an ovary were present on the corresponding sides. In 

 Bond's pheasant the male and female plumage was not so 

 sharply separated, and there was a gonad only on the left side ; 

 this gonad contained both ovarian and testicular tissue. At 

 first sight it seems impossible to explain such an abnormahty 

 by the hormone theory; both kinds of hormones circulate 

 in all parts of the body, and it would seem impossible to inter- 

 pret the sharp separation of the male and female plumage. 

 Most authors agree that the recorded condition of inter- 

 sexuality is "due to differences in the tissues of the body, and 

 the activity of the ovary or testis must be regarded rather as a 

 stimulus to their development than the source of origin" 

 (Doncaster, 1914, p. 99). The conclusion was drawn from 

 these observations that the tissues of the male normally differ 

 from those of the female. Doncaster assumed that "the 



