530 The American Naturalist. [June, 
Agriolimaz agrestis L. and A. melanocephalus Kal. (Babor, 1, 2). 
In the Opisthobranch Gasteropoda in Cymbulia (Leuckart, 27), 
Cymbuliopsis (Peck, 35); Desmopterus papilio (Chun, 8); Lobig- 
er, Clio striata, Clione, Eolis and Elysia (Pelseneer, 36, 37). 
Among the Lamellibranchiata in Ostrea (Davaine, 12, confirmed 
by Van Beneden, 45). Finally, among the Vertebrates in 
Myxine (Cunningham, 11, Nansen, 34), and in Chrysophrys 
(Brock, 6). 
Proterogynic Hermaphroditism is the term applied to the 
case of those animals, where the male and female gonads are 
not morphologically separate from each other, and where in 
the single ovotestis the female genital products are developed 
before the male products. It is much more restricted than the 
two other phases of Hermaphroditism under discussion, thus 
far having been observed only in pulmonate Gastropoda,— 
Limaz maximus L., Malacolimaz tenellus Nils. (Babor, 1, 2), Agrio- 
limax levis Müll. (Brock, 7; Babor, 1, 2); and among the 
Tunicata in Salpa (Krohn, 23; Korschelt and Heider, 22). 
Since now both Proterogynic and Protandric Hermaphro- 
ditism may occur in the same genus (e. g. Agriolimaz), these 
two phases of Hermaphroditism are probably closely allied. 
And as there exists in some cases of Protandry a cycle of 
development, where the individual is first male, then herma- 
phrodite, then female (e. g. Stichostemma) ; so there is present 
in some cases of Proterogyny (e. g. Agriolimax levis) a similar 
ontogenetic cycle, only reversed, by which the individual is 
first female, then hermaphrodite, and lastly becomes male. 
In fact, I think that I am justified in concluding, that the 
three forms of Hermaphroditism, which form the subject of 
the present paper, are closely connected with each other, and 
their differences are more of degree than of kind. 
What light does the consideration of these three phases of 
Hermaphroditism throw on the much discussed question,— 
whether in the Metazoa the hermaphroditic or whether the 
dioecious state should be regarded as the more primitive? 
Now we have found that in each phase, the products of the one 
sex develop earlier than the products of the other sex ; accord- 
ingly, judging from the well known biogenetic law, that the 
