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body, partly, also on the dorsal sides Pl. I, fig. 8, et., Pl. VIII, fig. 2, 3, 7). These I have designated, sub-ectodermal testes;
they have no communication with the true testes. The spermatozoa, developed in these testes, must pass through the
ectoderm to escape from the bod)-, vide Pl. VIII, fig. 3 a, b, c, d, f and fig. 2 b and c. These sub-ectodermal testes have a
somewhat peculiar structure. I have not observed distinct cell-membranes, but a great many nuclei are often situated close
together, and they have, thus, frequently, the appearance of a large cell with many nuclei, vide fig. 2 a. These
sub-ectodermal testes must be regarded, I think, as, originally, portions of the chief testes which have, probably, in the earliest stages
of development, a very extensive distribution through the whole body. When, however, the ovaries are developed, they
become restricted to a more confined distribution, and during this process some portions are isolated, and become, in the adult
specimens, sub-ectodermal testes, the spermatozoa of which are obliged to force their own passage from the bod}’. Among
the sparmatozoic globules, plenty ot undeveloped spermatocytes occur, in the vasa diferentia, as well as in the vcsiculæ
seminales and ductus ejaculatorii. The development of the penes varies vary much; in some species (e. g. M. giganteum
and M. graffi) they are very prominent, whilst in other species (M. cirriferum) they are scarcely visible, the ductus ejaculatorii
opening into no prominence.
Complemental males (Dwarf-males).
I have found complemental males in M. giganteum, M. gigas, and M. carpenteri. The structure in these males is
quite similar to that of the hermaphrodites, except that on the dorsal side, where the ovaries are situated, we have here, in
these, found testes whose cells are, however, little developed, and they have, frequently, thus, a partial resemblance to young
ovaries. Upon closer examination, however, it can be seen that they communicate with, and are parts of. the more
developed portion situated more to the centre of the body. The testes fill the entire body-cavity, so that but little of it is visible.
A feature of great interest in these males is the fact, that the three oviducts of the hermaphrodites are present, in them.
The dorsal oviduct (uterus) is but little developed, but the lateral oviducts are well developed, and quite resemble those of the
hermaphrodite, except that they contain no ova. — In branches of the uterus are situated some organs, similar to those in the
hermaphrodites (Pl. II, fig. 15, ovr.) and which are, probably, traces of ovaries. The presence of these oviducts can, in my opinion,
be explained in only one of two ways viz. These males are, either sprung from hermaphrodites and these oviducts are, then,
traces of their origin; or these males are only young hermaphrodites, and ovaries communicating with these oviducts are
subsequently developed, whilst the testes are restricted in their distribution. I have not, as vet, had a sufficient supply of
material to enable me to determine these questions. It is af eature of interest, that in the single male specimen of M.
carpenteri found I have observed cells, quite similar to young ova, situated on the dorsal side and, so far as I could discover,
situated between the testes and the connective-tissue of the body-wall. These cells must be, either, remnants of
hermaphrodites, or young ovaries which are subsequently developed.
The hermaphroditism of the Myzostomida.
The hermaphrodites of the Myzostomida are regarded by Beard as having a secondary origin, and he regards the
diecious forms to be primitive ones, or the starting point . I can not give my assent to that view, for the following reasons:
i) The diecious species are the most parasitic forms, and if Beard’s view, that the Myzostomidae have become hermaphrodites
because there is a tendency in parasitic life to produce hermaphroditism, is correct, it may, also, with some reason be
concluded, that the Myzostomida Cysticola or most parasitic species should, especially, be androgynous, but that is not the
case, for most of these species are diecious, whilst the most migrator)’ ones, and, consequently, least parasitic forms are,
especially, hermaphrodites; and the little migratory species are, on the other hand, provided with dwarf-males which
according to Beard’s view are more primitive than the hermaphrodites, and are remnants of a diecious state. The most parasitic forms,
and the little migrator)’ species with dwarf males, cannot be assumed to be the starting point of the migratory free-living
species. 2) The rudiments of testes visible in M. cysticolum are, to my mind, more probably, remnants of an androgynous
state1) than a budding development of male organs. If such rudiments, without male generative apertures, occur, uniformly, in
all females, I cannot conceive how they can be a budding development, as they can have 110 opportunity of sexual function.
Their regular occurrence cannot be accounted for, solely, by assuming a tendency in the ovaries to develope spermatozoa.
3) The males of the diecious species are smaller in relation to their females, than the dwarf-males are, 111 relation to their her-
Under such circumstances the male generalive aperlures, usually, disappear, as for instance in C’ymothoida.
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