The determination of sex in animal development. 715 



and it is but a step further to the sisting of their production by the 

 suppression of the male-eggs^), 



16. Hermaphroditism is a lower and simpler state than partheno- 

 genesis. As Feitz Müller, Brock, Yves Delage, Paul Pelseneer, 

 Maupas, and the writer have maintained for certain cases, and as 

 I would now generalize for all, functional hermaphroditism is a 

 peculiarity of the female sex alone. That is, as a rule only the 

 females of a species are capable of becoming hermaphrodite. 



17. The possibility of hermaphroditism depends on the property 

 possessed by the female Metazoon — and to all appearance by it 

 only — of "producing" two kinds of functional gametes, the male- 

 eggs and the female-eggs. 



18. In hermaphroditism, instead of the production and maturation 

 of two kinds of eggs, male and female in destination, we witness the 

 maturation and fertilisation of one kind only, the female-egg. The 

 germ-cells, which here should have become male-eggs, are converted 

 into spermatogonia and from these spermatozoa are ultimately pro- 

 duced 2) (Fig. C, page 750). 



With the table (in: Biol. Ctrbl., V. 22, p. 326), showing the 

 life- cycle of the skate, it is an easy matter, to see how this comes 

 about. Following the history of a male-egg in the skate from its 

 formation, through its fertilisation by a spermatozoon, to its 

 cleavage, we have from this a certain number, 256, primary germ- 

 cells arising. Of these 256 primary germ-cells one develops into 

 an embryo , while the remaining 255 ultimately go to form the 

 male "sexual products" of this embryo, its spermatozoa. In herma- 

 phroditism, instead of the fertilisation of male-eggs, their cleavage, 

 and the formation of primary germ-cells and embryo, we find the 

 omission of these, and the production of spermatozoa some cell- 

 generations earlier than would have been the case, had the said 

 male-egg been fertilised, and had it developed. In my researches on 

 the germ-cells the formation of an embryo has long been recognised 

 to be a mere incident in a complicated life-cycle — an incident arising 



1) Compare Section VIII, jDage 749. 



2) A diagram, made up of the left half of Fig. 1 from p.g.C to 

 the ripening of the female-egg and of the right half of Fig. 2 from 

 li.g.C to the ripening of the ordinary or hairlike spermatozoa, gives a 

 fair idea of what haj^pens in hermaphroditism; this has been depicted 

 in Fig. 3. 



Zool. Jahrb, XVI. Abth. f. Morph. 47 



