I4 2 GENERAL PRINCIPLES OF ZOOLOGY. 



a union of testes and ovary into a single glandular body or 

 hermaphroditic gland; our land-snails have an hermaph- 

 roditic gland, which in the same follicle produces sper- 

 matozoa and eggs. 



Occurrence of Hermaphroditism. Hermaphroditism 

 is, in general, of more frequent occurrence in the lowly- than 

 in the highly-organized animals. The insects and the 

 groups of vertebrates, the most developed classes of ani- 

 mals, are, almost without exception, of separate sexes; only 

 two cases of normal hermaphroditism are known among 



FIG. 69. Lateral hermaphroditism of a butterfly (Ocneria dispar). Left female, right male. 



(After Taschenberg.) 



them, the sea-perch, Serranus scriba, a bony fish, and Myx- 

 ine glutinosa, the Hag-fish. More commonly, hermaphro- 

 ditism is observed as an abnormality, usually in the form 

 of lateral hermaphroditism, in which one half of the animal 

 produces only male, the other half only female, sexual 

 glands. If the males and females of a species are distin- 

 guishable by their appearance, then lateral hermaphroditism 

 is expressed in their external form, since one half of the 

 animal has the characteristic marks of the male, the other 

 half those of the female. Hermaphroditic butterflies and 

 bees are known in which the male half bears the special 

 form of the male feelers, eyes, and wings, and thus is essen- 

 tially different from the female half (Fig. 69). 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. 



