GENERAL ORGANOLOGT. 119 



animal, some distance apart, as in the earthworm, in which two 

 segments are male, while a third segment is female (fig. 71). 

 More rarely there is a union of testes and ovary into a single 

 glandular body or hermaphroditic gland; our land-snails have an 

 hermaphroditic gland, which produces spermatozoa and eggs in 

 the same follicle. 



Occurrence of Hermaphroditism. Hermaphroditism is, in 

 general, of more frequent occurrence in the lower than in the 

 higher animals. Insects and vertebrates are, almost without 

 exception, dioecious; only two cases of normal hermaphroditism 

 are known among them, a sea-perch, Serranus scriba, a bony fish, 

 and Myxine glutinosa, the hagfish. More commonly hermaph- 

 roditism occurs as an abnormality; a striking form is lateral 

 hermaphroditism, in which one half of the animal has only male, 

 the other half only female, gonads. If the males and females of 

 a species be distinguishable by their appearance, then lateral 

 hermaphroditism is expressed in their external form, since one half 



FIG. 72. Lateral hermaphroditism of a gipsy moth (Ocneria dispar). Left female, 

 right male. (After Taschenherg.) 



of the animal has the characteristic marks of the male, the other 

 half those of the female. Hermaphroditic lepidoptera and bees 

 are known in which the male half bears the special form of the 

 male antennas, eyes, and wings, and thus is essentially different from 

 the female half (fig. 72). Still it must be noted here that, in 

 many instances where the external appearance pointed towards 

 hermaphroditism, anatomical investigation has disclosed either 

 only male or only female sexual glands in a rudimentary condition 

 (gynandromorphism). True hermaphroditism (the presence of 

 both kinds of sexual glands in the same animal) is extremely rare 

 in mammals and in man. What is described as hermaphroditism 

 does not in the majority of cases deserve the name. 



