The Sexual Conditions of Myzostoma glabruni (F. S. Leuckart). 301 



remnants of hermaphroditism or the first development of female organs 

 (in a young stage): the dwarf males are, consequently, only young 

 herraaphrodites. I thiuk it is indeed most probable that some herma- 

 phrodites, at ali events in their youth, perform exclusively a male 

 function. Finally, if it is the case, as Beard supposes, that the 

 dvvarf-males are primordial and the dicecious state the primary one, 

 then the hermaphrodites must bave been developed from males, and 

 not from females as Beard supposes«. 



It may be well to take seriatim the Statements made in the above 

 summary. Our author creates artificial distinctions in the parasitism 

 of the different species of Myzostoma. According to bis conceptions 

 the cystic forms are the most parasitic, those, like M. cirriferum^ 

 which wander freely about on the host, are least parasitic, while 

 tbe fixed, but non-encysted, forms, like M. glabrmn, occupy an inter- 

 mediate Position between the extremes of the parasitism. To my 

 mind there is little or no difference in the degree of parasitism in 

 ali these cases. To whatever species of the genus it belongs, the 

 individuai Myzostoma probably spends its whole post-larval life on 

 one individuai host. It may be assumed that the parasitism was 

 introduced for the good of the species, for its preservatiou. A fixed 

 form, and especially an encysted one like M. cysticolum, it not so 

 liable to destruction, as is a form, which can roam freely about 

 within a circumscribed area. Individuals of M. cirriferum must always 

 be in great danger of being either washed away or devoured by the 

 host. The great abundance of M. cirriferum may be taken to be a 

 provision against these dangers, but it is no doubt also due to the 

 small size of the animai and its freedom of motion, for these two 

 conditions admit of a much greater infection of one individuai host, 

 than do the corresponding conditions of life in M. glabrum. The 

 objection that the least migratory forms cannot be assumed to bave 

 been the starting point of the migratory free-moving species is beside 

 the point. It would only be relevant, if it were held, that the fixed 

 and encysted forms resembled the ancestors of the free hermaphrodite 

 species. We do not know what these ancestors were like, and ali 

 that is maintained is, that they must bave been dicecious — that 

 ali originai Myzostomid?e were once free non-parasitic forms is, of 

 course, not open to question. 



Regarding the rudiments of festes in M. cysticolum^ as described 

 by VON Graff, an assumption that they are a »budding development« 

 is quite as justifiable as oce to the contrary. Too much weight should 



