It should be observed that the evidence in this summary is of a cumulative nature. If we think it highly, or in some degree probable,--from the ordinary form of _Ibla Cumingii_ having been shown on good evidence to be exclusively female,--from the absence of ova and ovaria in the assumed males of both species of Ibla, at the period when their vesiculæ seminales were gorged with spermatozoa,--from the close general resemblance between the parts of the mouth in the parasites and in the Iblas to which they are attached,--from the differences between the two parasites being strictly analogous to the differences between the two species of Ibla,--from the generic character of their prehensile antennæ,--and from other such points,--if from these several considerations, we admit that these parasites really are the males of the two species to which they adhere, then in some degree the occurrence of parasitic males in the allied genus Scalpellum is rendered more probable. So the absolute similarity in the antennæ of the males and hermaphrodites both in _S. vulgare_ and _S. Peronii_; and such relations as that of the relative villosity of the several species in this same genus, all in return strengthen the case in Ibla. Again, the six-valved parasites of _S. Peronii_ and _S. villosum_ are so closely similar, that their nature, whatever it may be, must be the same; hence we may add up the evidence derived from the identity of the antennæ in the parasite and hermaphrodite _S. Peronii_, with that from the antennæ in the male _S. villosum_, approaching in character to Pollicipes, to which genus the hermaphrodite is so closely allied; and to this evidence, again, may be added the singular coincident absence of caudal appendages in the male and hermaphrodite _S. villosum_. If these two six-valved parasites be received as the complemental males of their respective species, no one, probably, will doubt regarding the nature of the parasite of _S. rostratum_, in which the direct evidence is the weakest; but even in this case, the particular point of attachment, and the state of development of the valves, form a link connecting in some degree, the parasites of the first three species with the last two species of Scalpellum, in accordance with the affinities of the hermaphrodites.