76 



THE EVOLUTION OF SEX. 



SUMMARY. 



I. Hermaphroditism is the union of the two sexual functions in one 

 organism. This occurs, however, in varying degrees. 



II. Embryonic hermaphroditism is probably a general fact with even 

 unisexual animals. It is certain in some cases. 



III. Casual or abnormal hermaphroditism is not infrequent. 



IV. Partial hermaphroditism (not involving the essential organs) is 

 exceedingly common. 



V. Normal adult hermaphroditism ; review of its occurrence. 



VI. True hermaphroditism occurs in many degrees of intimacy. 



VII. Self-fertilization is a rare exception among animals ; commoner in 



plants. 



VIII. " Complemental males "—pigmies attached to hermaphrodites — 



occur in two groups. 



IX. The conditions of hermaphroditism, in part, involve a surplus of 

 material. 



X. Hermaphroditism is primitive ; the unisexual state is a subsequent 

 differentiation. The present cases of normal hermaphroditism imply either 

 persistence or reversion. 



LITERATURE. 



See already cited works of 

 Gegenbaur, Hensen, Hertwig, Hatchett Jackson and Rolleston, 



passim. 

 Bourne. — On Certain Abnormalities in the Common Frog. i. The Occurrence 



of an Ovotestis. Quart. Journ. Micr. Sci., XXIV. 

 Brock. — Morph. Jahrb., IV. Beitrage zur Anatomic und Histologic der 



Geschlechtsorgane der Knochenfische. 

 Giles.— Quart. Journ. Micr. Sci. 1888. 

 Laulanie, F.— Comptes Rendus, CI. (1885), pp. 393-5. 

 Marshall, A. Milnes. — On Certain Abnormal Conditions of the Reproductive 



Organs in the Frog. Journ. Anat. Physiol., XVIII., pp. 121-44. 

 Meehan, T. — On Self-Fertilization and Cross-Fertilization in Flowers. Penn. 



Monthly, VII. (1876), pp. 834-43. 

 Pfluger, E. — Archiv. ges. Physiol., XXIX. 

 Simpson, J. Y. — Todd's Cyclopedia of Anatomy and Physiology. Art. 



Hermaphroditism, pp. 684-738 (1836-9). 

 Spengel. — Arb. Wiirzburg, III., 1876. Ueber d. Urogenital System der 



Amphibien. 



Zwitterbildung bei Amphibien. Biol. Centrlbl., IV., 8, cf. 9. 



Sutton, J. B. — Hypertrophy and its Value in Evolution. Proc. Zool. Soc, 



London, 1888, pp. 432. 

 General Pathology. London, 1886. 



