HERMAPHRODITISM. 67 



on the other, or male anteriorly and female posteriorly. Sir J. W. 

 Simpson, in a learned article on the subject, has distinguished cases of true 

 hermaphroditism according to the position of the organs, into lateral, 

 transverse, and vertical or double. Among invertebrates the same has 

 been occasionally observed, especially among butterflies where striking 

 differences in the colouring of the wings on the two sides have in some 

 cases been found to correspond to an internal co-existence of ovary and 

 testis. The same has been observed in a lobster, and is probably 

 commoner than the recorded cases warrant one in asserting. As low down as 

 coelenterates, casual hermaphroditism may occur, as F. E. Schulze showed 

 in one of the medusoids. 



§4. Partial Hermaphroditism. — Kx\. organism may be said to be truly 

 hermaphrodite when both male and female organs are present, or when, 

 without there being separate organs, both male and female elements are 

 produced. It is then both anatomically and physiologically hermaphro- 

 dite, and of this, as we shall see, there are abundant illustrations among 

 lower animals. Snail, earthworm, and leech are examples of this hermaph- 

 roditism, in varying degrees of intimacy. 



But, as we have just noticed, a species normally unisexual may occasion- 

 ally exhibit hermaphrodite individuals. In these only one of the double 

 essential organs may be functional, or both may be sterile. Whether 

 physiologically or not, such animals are anatomically hermaphrodite. Both 

 kinds of essential organs are at least present. 



To those must now be added a further series of cases to which the term 

 partial hermaphroditism seems most applicable. Only one kind of sexual 

 organ, ovarj- or testis, is developed ; but while one sex preponderates, there 

 are more or less emphatic hints of the other. As the reproductive organs 

 are to be regarded as the most important, but not by any means the sole 

 expression of the fundamental sex-differences, it is impossible to separate 

 partial hermaphroditism by any hard and fast line from the above, and 

 from the next set of cases (paragraphs 3 and 5). Almost all cases of partial 

 hermaphroditism occur as exceptions, though a few are constant. 



In the higher animals, partial hermaphroditism is usually expressed in 

 the nature of the reproductive ducts. In this connection the structural 

 resemblance of the male and female organs must be once more emphasised. 

 Even the Greeks had their vague and fanciful theories of what we now call 

 the homology of the reproductive organs and ducts in the two sexes. 

 Through the labours of the anatomists of Cuvier's school, such as his fellow- 

 worker Geoffroy St Hilaire, and yet more through more recent embryo- 

 logical discoveries, there is now both clearness and certainty as to the main 

 facts. The reproductive organs proper, the ducts, and the external parts, 

 are developed upon the same plan in male and female. Thus, except in 

 the lowest vertebrates, what serves as an oviduct in the female, is equally 

 present in the embryo male, and persists in the adult as a more or less 

 functionless rudiment. In the same way, what serves as the duct for the 

 sperms {vas deferens) in the male, is equally present in the embryo female, 

 and persists in the adult as a rudiment, or is diverted to some other pur- 

 pose. This is a perfectly normal occurrence, dependent upon the embryo- 

 logical history of the ducts in question. It is necessary, however, to realise 

 both the primitive resemblance and the fundamental unity of the two sets 

 of organs, in order to understand how partial hermaphroditism is so fre- 

 quent, and also to distinguish it from " spurious hermaphroditism," where 



