The Sexual Conditions of Myzostoma glabrum (F. S. Leuckart). 309 



afforded by the presence of »ovaries« in the dorsicolous forms. Of 

 the existence of these structures there cannot be the slightest doubt 

 — as to their interpretation, that is another mattei'. 



If it cau be shown that these structures, Nansen's organs, are 

 invariably ovaiian in nature in the dorsicolous forms, as well as in 

 the hermaphrodites, it, of course, follows that the dorsicolous forms 

 of M. glahrum are not complemental males. 



I bave closely examined these structures in my own dorsicolous 

 specimens, and can find no particle of evidence to show that they 

 are ovaries. From the minute structure of the component cells it 

 appears to me to be far more likely that they represent the originai 

 testes, for the cells bear a dose resemblance to, amounting to identity 

 with, the groups of sperm-mother-cells, »seattered« about in various 

 places. But Wheelp:r brings forward what, though far too vaguely 

 stated for its importance, appears to be positive evidence of the 

 ovarian nature of Nansen's organs in dorsicolous forms. In fig. 56 

 he figures a large ^^^^ Ijing" on the outer side of oue of these 

 structures, and on pag. 241 he reraarks: — »specimens in this stage 

 (6 a, 1 mm long) are found, like those of the five preceding stages, 



attached to the backs of older individuals In some of the 



specimens a few of the oocytes bave begun their growth while stili 

 in the ovary (compare pi. 12, fig. 56 e/)«. 



In this passage and in the description of the piate it is not 

 distinctly stated, that this figure is taken from a true 

 dorsicolous specimen of M. glabrum. The reader is left to 

 iufer that this was really the case, and the author leaves a loop- 

 hole to doubt, where tlie Observation, which of ali others would 

 decide the matter, is concerned. A precise statement as to the place, 

 from which the specimen was taken, as to the number of such ap- 

 parently hermaphrodite dorsicolous forms in the author's possession, 

 and as to the number of obvious eggs in each of these, might bave 

 settled the point for good. I would submit that Wheeler may bave 

 been mJstaken in referring this figure to a true dorsicolous specimen 

 of il/, glahrum. It may be suspected that it was taken from the 

 side wall of a hermaphrodite, and, as I recognised in 1884, such 

 specimens are uever true males, but always contain eggs, as weil as 

 spermatozoa. From the size of the e^^., taken in conjunction with 

 what I bave said in preceding pages as to the development of eggs 

 in small disc-forms of 0.75 mm and under, it is probable that this 

 specimen contained a considerable number of eggs, and it, and any 



