300 J- Beard 



In both males and hermapbrodites, dovsicolous and disc-forms, 

 the neural eoelomic epithelium is composed of the forerunners of 

 male cells, and in the males the hiiemal peritoneum is made up of 

 similar cells. In the hermaphrodites, on the other hand, the latter 

 portion of the eoelomic wall is almost eutirely concerned in the pro- 

 duction of egg-cells. A few cells ma}^, however, give rise to sper- 

 matic Clements (fig. 5). 



On pag. 79 of his memoir Nansen has summarised bis objections 

 to the view of the secondary or derived nature of the hermaphro- 

 ditism of M. glabrum. 



He writes: — »the dioecious species are the most parasitic forms, 

 and if Beard's view, that the Myzostomidaj bave become herma- 

 pbrodites, because there is a tendency in parasitic life to produce 

 hermaphroditism, is correct, it may, also, with some reason be con- 

 cluded that the Myzostomida Cysticola, or most parasitic species, 

 should especially be androgynous, but that is not the case; for most 

 of these species are dicecious, whilst the most migratory ones, and 

 consequently least parasitic forms, are especially hermaphrodites: and 

 the little migratory species are, on the other band, provided with 

 dwarf males, which, according to Beards view, are more primitive 

 than the hermapbrodites, and are remnants of a dioecious state. The 

 most parasitic forms, and the little migratory species with dwarf 

 males cannot be assumed to be the starting point of the migratory 

 free-living species. The rudiments of testes visible in 31. cysticolum 

 are, to my mind, more probably remnants of an androgynous state 

 than a buddiog development of male organs. If such rudiments, 

 witbout male generative apertures, occur uniformly in all females, 

 I cannot conceive how they can be a budding development, as they 

 can bave no opportunity of sexual function. Their regulär occurrence 

 cannot be accounted for solely by assuming a tendency in the ovaries 

 to develop spermatozoa. The males of the dioecious species are 

 smaller in relation to their females than the dwarf males are in re- 

 lation to their hermaphrodites. If these males are about to become 

 extinct, the contrary might be expected to be the case. The structure 

 of the dwarf-males indicates, in one way or other, a relationship to 

 the hermaphrodites. If the dwarf-males are more primitive than the 

 hermaphrodites, I cannot account for the presence of oviducts. As 

 above mentioned, I conclude that these oviducts must really be, either 



