eyes, curious prehensile antennae, closed
rudimentary mouth and six natatory legs so different from those in the
first stage:--we have the two attached males, with their bodies reduced
almost to a mouth placed on the summit of a peduncle, with a minute,
apparently single eye shining through the integuments, without any
carapace or capitulum, and with the thorax as well as the legs or cirri
rudimentary and functionless:--lastly, we have the hermaphrodite, with
all its complicated organisation, its thorax supporting six pairs of
multi-articulated two-armed cirri, and its well-developed capitulum
furnished with horny valves, surrounding this wonderful assemblage of
beings. Unquestionably, without a rigid examination, these four forms
would have been ranked in different families, if not orders, of the
articulated kingdom.

_Concluding Remarks._--If the creature which I have considered as the
male of _Ibla Cumingii_ be really so, and the evidence formerly given
seems to me amply conclusive, then the animal just described, from its
close affinity in every point of structure with the former, assuredly is
the male of _Ibla quadrivalvis_. But feeling strongly how improbable it
is, that an additional or complemental male should be associated with an
hermaphrodite, I will make a few remarks on the only possible
hypothesis, if my view be rejected,--namely, that the two parasites
considered by me to be exclusively males, are not so, but are
independent hermaphrodite Cirripedes, the female organs and ova (which,
if present, would have been nearly mature, judging from the presence of
spermatozoa in both species) having been overlooked by me in every
specimen: and again, that in the animal described as the female _I.
Cumingii_, I have, though minutely dissecting several specimens, and
finding far smaller parts, such as the organs of sense and nervous
system, entirely overlooked all the conspicuous male organs, though when
I came to _I. quadrivalvis_, and naturally expected to find it likewise
exclusively female, a single glance showed me the great probosciformed
penis, and by the simplest dissection the vesiculae seminales and testes
were exhibited. Such an oversight is scarcely credible; but even if
assumed, we have to believe in the extraordinary circumstance of the two
parasites being species of an independent genus, not only the very next
in alliance to the animals to which they are attached, but in certain
most important points,