the Theory of Dwarf Males to Myzostoma. 379 



In these the dwarf males never become sexually mature, 

 being represented by the Cypris larvae found on the young 

 Sacculina externa. 



Smith believes that both these Cypris larvae and the com- 

 plemental males of the Pedunculata are potential hermaphro- 

 dites, in which development is arrested because of the position 

 taken up by them on fully developed individuals of the same 

 species. 



This idea is supported by what occurs in the Epicarida, 

 a group of parasitic Isopods. Here all individuals are at first 

 larval males, which, after crawling upon the adult (function- 

 ally female) individuals and fertilizing them, migrate to and 

 become parasitic upon their hosts — various Crustacea, — and 

 there assume the female condition. 



They are therefore protandric hermaphrodites. 

 Quite recently Orton has brought forward evidence of the 

 same sort of thing in Crepidula, and he has expressly 

 accepted Smith's theory as an explanation. 



The facts known about Myzostoma seem to be susceptible 

 of a similar interpretation, whether we accept Beard's or 

 Wheeler's account of their life- history. 



In the former case, the sexual relations of Myzostoma are 

 exactly comparable with those of the Pedunculata ; in the 

 latter they are mure like those of the Epicarida. 



Beard described the dwarf dorsicolous males as never at 

 any time showing traces of ovaries, while individuals found 

 on the disc of the Comatula host have both ovaries and testes, 

 even though they be smaller than the largest dorsicolous 

 specimens. He therefore claimed that these are true com- 

 plemental males. 



Wheeler traversed this statement and said that the ovaries 

 can always be found, even in the youngest dorsicolous indi- 

 viduals. He identified them with Nansen's " problematical 

 organs." 



Working on this assumption, he noted a gradual increase 

 in size and activity in the ovary; and he was able to trace the 

 animal through all stages, from the time when neither mature 

 sperms, or only a very few, nor ova were present, to an 

 almost purely female state, passing on the way through a 

 stage when numerous mature sperms, but only immature 

 ova, were present, followed by a completely hermaphrodite 

 condition. 



In spite of some criticisms from Beard, Wheeler's state- 

 ments seem to be quite unshaken, and his evidence, both as 

 regards descriptions and drawings, has all the appearance of 

 being a more trustworthv guide to the real state of things. 



26* 



