716 JOHN BEARD, 



for a certain end — the creation of a harbour of refuge for a set 

 of germ-cells. In hermaphroditism Nature dispenses with this incident 

 in the cases of male-eggs, and they become converted into spermatozoa 

 within a gametozoou or sexual generation, older than that, in which 

 they ought to have arisen. From the new light, thrown by my 

 researches upon hermaphroditism, the late Fritz Mueller ^), and the 

 writer 2) were clearly in the right in disputing the validity of current 

 views of the nature of hermaphroditism ^). We denied, that herma- 

 phroditism was the original condition, which prevailed prior to the 

 evolution of separate sexes, and we regarded it as derivable from 

 the dioecious state '^). The opposite opinions were, and still are, 

 maintained by leading zoological authorities. 



19. A comparison of parthenogenesis and hermaphroditism de- 

 monstrates, that in the former there is what may be termed a pre- 

 cocious development of an embryo, male or female, in the latter the 

 precocious development of male-eggs or their forerunners to form 

 male gametes or spermatozoa without the intermediation of the other- 

 wise necessary male embryo or sexual person. In hermaphroditism 

 the males tend to disappear, because the male-eggs, which should 

 have gone to form them, have been used in the development of sper- 

 matozoa. In parthenogenesis the males disappear for another reason, 

 because their production may become unnecessary. 



1) Müller, Fritz, Die Zwitterbildung im Thierreich, in : Kosmos, 

 V. 2, 1885, p. 321—334. 



2) Beard, J., The life-history and development of the genus Myzo- 

 stoma, in: Mitth. zool. Stat. Neapel, V. 5, 1884, p. 544—580, 2 pi. 



3) Ordinary hermaphrodites might be defined as "Metazoan persons 

 of one kind, each bearing germ-cells of two sorts". They would then 

 be in contrast with dioecious forms, where there were two kinds of in- 

 dividuals, carrying germ-cells of four sorts, two for each description of 

 individual. A definition of this character might have made clear the nature 

 of the hermaphrodite person, for, where in hermaphroditism in animals 

 a second kind of person is encountered, this is a male, the so-called 

 'complemental male'. 



4) In 1884 the writer in an inaugural dissertation showed, that in 

 Myzostoma and the Cirripedia hermaphroditism had been secondarily 

 superimposed upon the females, and, independently in 1884 Yves De- 

 LAOE arrived at the like conclusion for Sacculina. This origin of herm- 

 aphrodites from what were really female Metazoa was extended to the 

 Mollusca by Paul Pelseneer in 1895. More recently still E. Maupas 

 has found it also to hold good for certain Nematodes (vide : E. Maupas, 

 Modes et formes de reproduction des Nematodes, in : Arch. Zool. expér., 

 V. 8, 1900, p. 463—624, 11 pi., I c. 582 et seq.). 



