62 THE EVOLUTION OF SEX. 



hermaphrodite, the male being furnished with a rudimentary ovary 

 in front of the testes. A similar hermaphroditism is not at all infre- 

 quent in cod, herring, mackerel, and many other fishes; while slightly 

 lower down in the series it occurs in the hagfish {Myxine). Some- 

 times a fish is male on one side, female 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 coloring of the wings on the two sides have in some cases 

 been found to correspond to an internal coexistence 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 ccelenterates, casual hermaphroditism may occur, as F. E. 

 Schulze showed in one of the medusoids. 



IV. Partial Hermaphroditism. — An 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 physio- 

 logically hermaphrodite; and of this, as we shall see, there are 

 abundant illustrations among lower animals. Snail, earthworm, and 

 leech are examples of this hermaphroditism, in varying degrees 01 

 intimacy. 



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

 occasionally exhibit hermaphrodite individuals. In these only one oi 

 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, ovary or testis, is developed; but while one sex pre- 

 ponderates, 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-differ- 

 ences, it is impossible to separate partial hermaphroditism by any hard 

 and fast line from the above, and from the next set of cases (para- 

 graphs III and V). 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 emphasized. Even the Greeks had their vague and fanciful 



