The >Sexual Conditions of Myzostoma glabrum (F. S. Leuckart). 313 



developed eggs arise from cells of the dorsal Peritoneum and not 

 from Nansen's organs. As apparently he has uever examined forms 

 from the disc under 1 mm the marked difference in outward shape 

 and in section between dorsieolous and disc-forms of 1 mm and under 

 has escaped him. 



The transformation is assigned to a definite stage, that of 1 mm, 

 and it is only afterwards that, with the faets of my two small tables 

 before him, he is forced to make a nevv assumption, that of eonsider- 

 able latitude in the attainment of »sexual maturity«. But what does 

 he understand by sexual maturity? On pag. 265, where the matter 

 is discussed, there is no definition of it given; but, from the drift 

 of the argument, it is obvious, that in this case Wheeler does not 

 consider the individuai to be sexually mature, until it has developed 

 ovaries, as well as testes. 



There would seera, however, to be no escape from the cou- 

 clusion, that an individuai M. glabrum is sexually mature, when it 

 contains ripe spermatozoa, and this is alraost certainly the case in 

 ali specimens over 0.5 mm in leugth. 



I am not aware, that I bave ever argued the question, as to 

 the period, when »sexual maturity« occurs in M. glabrum — ali I 

 bave dealt with has been the trifliog problem of the sizes of specimens 

 in which eggs as well as ripe spermatozoa were first to be found. 



Wheeler's results give him this size as about 1 mm, and the 

 only case figured by him may be challenged, among other grounds, 

 on that, that the egg depicted is far too big to ha\e just come iuto 

 existence. My table 2 thus casts considerable doubt on the correctuess 

 of his'conclusion. Does the author ask us to belle ve, that an q'^'^ 

 of that size has just escaped from Nansen's ovary? Its actual 

 diameter is rather more than 0.028 mm, whereas the largest eggs 

 from an incipient hermaphrodite from the disc (such as those shown 

 in fig. 1) measure only 0.006 mm in diameter! 



Nothing is further from my mind, than any idea of maintaining 

 the male nature of the dorsieolous forms, if there be any evidence 

 directly contradicting this. The whole matter appears to me so 

 trifling, that, having far more congenial and important work in 

 band, I should not feel called upon to discuss it, were it not, that 

 observations of mine, of whose correctness new search has again 

 and again convinced me, had been declared baseless on grounds of 

 the most fallacious character. 



Nor is entry into the fìekl of controversy rendered more inviting 



