The Sexual Phases of Myzostoma. 
243 
given above: M. glahrum is dioecious from tbe time its reproductive 
Organs first api)ear, and like M. cirriferum it is functionally male 
in early life, then functionally hermaphrodite and finally function- 
ally female in its senile stages. The correlation of tbe migration to 
tbe disc of tbe Antedon and tbe development of functional berma- 
phroditism is not by any means perfect, since it is possible to find 
functional male individuals on tbe disc of tbe Antedon^ and inci- 
piently hermaphrodite individuals still attached to tbe back and sides 
of tbe older Myzostomes. But in general it may be said tbat tbe 
change from tbe functional male to tbe functional hermaphrodite oc- 
curs when tbe animal shifts its position to tbe disc. 
! 4. AL alatum^ v. Graff. 
In form and habits tbis species closely resembles M. glahrum, 
My observations were made on half a dozen specimens obtained from 
tbe discs of a few Antedon phalangium,, Müller. Tbe young are found 
attached to tbe anterior dorsal surface of tbe older individuals. Tbe 
ovary and testes are almost exactly like those of M. glahrum^ so tbat 
I may dispense with a special description and figures. The young 
individuals are functionally male, tbe larger ones functionally herma- 
phrodite. I have not seen any functionally female specimens, but doubt 
j not tbat they occur. 
I Prouho’s observations ('92) on tbis species, tbougb incomplete 
in some particulars, were evidently made on more material tban I 
have been able to secure, and as tbey offer very valuable Support 
to my Interpretation of tbe sexual phases of tbe Myzostomidae, I 
may quote tbem here. 
He says: »On trouve, en effet, tres frequemment, sur le dos du 
M. alatum^ de soi-disant mäles complementaires, au nombre de un 
ou deux, rappelant exactement ceux qui ont ete decrits par M. Beakd 
cbez le Myzostoma glahrum et que M. v. Graff avait eii probable- 
ment raison de considerer comme des jeunes. Or une Serie d’obser- 
vations m’a montre, sans aucun doute possible, que les individus 
fixes sur les dos du Myzostoma alatum hermaphrodite sont de 
petits Myzostomes de son espece qui, mäles dans leur jeune äge, 
avec spermatozoides bien developpes et conduits deferents pareils ä 
ceux de Tadulte, grandissent et acquierent, en grossissant, 
des ovaires identiques ä ceux de Tbermapbrodite qui les 
Supporte, et cela sans abandonner les dos de ce dernier.a 
Mittheilungen a. d. Zoolog. Station zu Neapel. Bd. 12. 17 
