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92
maphrodites. If these males were about to become extinct, the contrary might be expected to be the case. 4) The structure of
the dwarf-males indicates, in one way or other, a relationship to the hermaphrodites. If the dwarf-males are more primitive than
the hermaphro lites, I cannot account for the pesence of oviducts. As above mentioned, I conclude that these oviducts must
really be, either, remnants of hermaphroditism, or, the first development of female organs (in a young stage); the dwarf-males are,
consequently, only young hermaphrodites. I think it is, indeed, most probable that some hermaphrodites, at all events in
their youth, perform, exclusively, a male function. Finally, if it is the case as Beard supposes, that the dwarf-males are
primordial and the diecious state the primary one, then the hermaphrodites must have been developed from males, and not
from females as Beard supposes. I think, in fact, that the view of hermaphroditism being, in all cases, the primitive state is
not so imamilable as hitherto supposed. It cannot be denied that, in many cases, there is some support for the view, that in
parasitic life there is a tendency to produce hermaphroditism, as Yves Delage in his Report on the Evolution de la
Saccu-line has stated. In the Myzostomidae, however, there is nothing found in support 0/ the probability of that view. If,
however, it can be assumed that hermaphroditism may be developed from gonochorism, then, gonochorism may again also, be
developed from hermaphroditism; there must, in both cases, exist a latent capability to form the other state, and
I think, indeed, that both states have been present in the most primary stage, and have kept pace with each other,
upwards, in the animal series. That hermaphroditism is, principally, produced by parasitism can not be assumed, because
there are a great many hermaphrodites which are not parasites, e. g. Oligochaeta, Polygordidae, Tardigrada etc. whilst,
on the other hand, there are many parasites which are not hermaphrodites e. g. Myzostomida Cysticola, Histriodrilus etc., it
may, also, be said that Cymothoidae are, to a certain extent, diecious; at all events they are not true hermaphrodites. The
question of the origin of the hermaphroditism and gonochorism is by no means exhausted, and we have not heard the
last of it.
Systematic position.
I cannot agree with Beard in regarding the Myzostomida as belonging to the Chaetopods; there are too many
dissimilar features in their structure, and I do not think that their development, as described by Beard, is quite that of a
Chae-topod . The absence of a praeoral ring of cilia, the relatively small development of the praeoral lobe, and the great
development of the body-part of the larva are no insignificant differences; they show that the larva is not a little
differentiated. The presence of a praeanal ring of cilia is common to most Annelid-larvae, and larvae of Mollusca, Bryozoa
etc. also posess such a ring, usually. In the absence of this ring, as well as in the rudimentary development of the praeoral
lobe, the larvae cf Myzostomida resemble those of Sipunculus; in their general structure there is, however, but little resemblance
to be traced. I am inclined to regard the Myzostomida as a peculiar, distinct, group belonging to the Annelids; related to the
Chaetopods but, also, showing a tendency towards some of the Arachnids (Linguatulida, Tardigrada and perhaps Pycnogonida)
and Crustaceans; they are sprung from the Trochophora; among the Archiannelids, their progenitor has been, chiefly, related to
that of Histriodrilus; on the other hand, it has, also, been related to that of the Arthropods, because the Myzostomidae show,
really, in their structure, a tendency towards these. They are, therefore, one of those groups presenting the greatest interest
as a subject for phylogenetic studies.
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