244 
W. M. Wheeler 
The latter part of this qnotation is worthy of particular atten- 
tion. Prouho did not see the true ovaries and what he designates 
as such are the »ovaries« of other writers, viz. the masses of eggs 
accumiilated in the branching body-cavity. Prouho's remarks are 
of interest because they show that in M. alatum the migration to 
the disc of the Antedon may be delayed tili the aniraals are plainly 
herraaphrodite. 
1 have had no difficulty in finding the true ovaries, one on 
either side of the intestine, in a small individuai attached to the 
back of an adult M. alatum. The structure of these organs is too 
much like that of the ovaries of If. glahrum in the corresponding 
period of growth (stage 7) to require special description. 
This peculiar habit of the young specimens settling on the older 
ones is not confined to M, glahrum and alatum, It occurs also in 
M. horologium^ v. Graff, parasi tic on Actinometra juhesi and A. strata^ 
as may be concluded from v. Graff's PL 1 Fig. 14 ('84 b). In describ- 
ing the species at pag. 28 he says: »The sexual organs resemble 
those of the last mentioned species [M. glahrum) and the young are 
attached to the body of the adult in the same way.« 
Three of the species studied by Nansen ('85), viz.: Myzostoma 
gigas, Lütken, giganteum^ Nansen, and carpenteria v. Graff, also agree 
with the above mentioned species in carrying the young. Nansen 
also infers, and I quite agree with him, that the same habit may 
occur in most sedentary species, like M. cJiinesicum^ v. Graff, testudo^ 
V. Graff, ecliinus^ v. GrafF, and compressum^ v. Graff. 
5. M. platypus^ v. Graff. 
This interesting species was described and figured by v. Graff 
('87, pag. 13 and 14, PI. 3 Figs. 7 and 8 and 9—12) from a single 
specimen taken from a leather-like uncalcified cyst on a specimen 
of Actinometra nohilis from Samboangan. v. Graff refrained from 
sectioning the type specimen and confined himself to a description of 
its external characters. On looking over the specimens of Actino- 
metra nohilis in the S. Kensington Museum I happened upon one which 
had the disc and bases of the arms covered with soft elliptical cysts. 
Nine of these cysts were opened and each was found to contain a 
single large specimen of M. platypus. Eight of the specimens were 
sectioned in the hope of finding differences in the development of 
the reproductive organs, but unfortunately all of them were almost 
exactly of the same age. 
