The Sexual Phases of Myzostoma. 
261 
y. Graff's rather guarded remarks on tliese species in the paper to 
which Beard evidently refers ('84 a). 
Beard's Interpretation of the small individuai» as »complemental 
males« was accepted by Nansen ('85), who succeeded in fìnding them 
also in the three species which he studied. Nansen, however, 
dissents from Beard's general conclusion regarding the origin of 
hermaphroditism in the Metazoa. 
In a short paper of recent date ('92) Prouho undertook to show 
that the small individuals attached to the large hermaphrodite spe- 
cimens of M. alatum are really young hermaphrodites in which the 
female organs have not yet developed, and he goes on to say: »Je 
n'ai pas eucore la preuve que les màles complémentaires dii M.glahrum 
acquièrent, eux aussi, des ovaires, mais ce que j'ai observé chez le 
M. alatum me porte à le croire.(c From his observations on M. 
puUinar he concluded that this species is dioecious. He tabulates 
the Mediterranean species of Myzostoma thus: 
»Type hermaphrodite M. cirriferum 
» » protérandre M. alatum 
» )) avec male complémentaire (?) M. glahrum 
» dioique avec male pygmé M. pulvinam. 
Such startling sexual variations occurring within the limits of 
a single genus can lead to only one of two reflexions: either we 
must bave bere a very unusual instability of sex, or there must be 
something radically wrong about the accepted accounts of Myzostome 
anatomy. Most authors bave tacitly accepted the former alternative 
and bave placed too implicit confìdence in their Interpretation of the 
reproductive organs. A more careful study of these organs, especially 
of the female organs, puts the whole question in a different light. 
Ali preceding authors bave been led astray by regarding the general 
peritoneal epithelium or general parenchyma as giving rìse to the 
ova, wbereas these elements are produced only by a very restricted 
portion of the peritoneal epithelium, which may be readily compared 
with the ovaries of Annelids, Vertebrates, etc. Even recent authors 
like Beard and Prouho would probably agree with Braun who, in 
a resumé of the work done on Myzostomes up to 1888, defines the 
ovaries thus (pag. 213): »Die Ovarien stellen 7 — 8 Paar verästelte, 
zwischen den Darmblindsäckchen und Hoden gelegene Schläuche dar, 
die sich manchmal bis zum Scheibenrand erstrecken und alle seitlich 
an einem gemeinschaftlichen, median verlaufenden, weiten Canal an- 
sitzen, dem Uterus.« The true condition of affairs must bave been 
18* 
