One finds general proof of the female's primitivity in the extreme smallness of certain male invertebrates, so tiny indeed that one can only consider them as autonomous masculine organs, or even as spermatozoides. The male of the syngames (an internal parasite of birds) is less a creature than an appendix; he remains in constant contact with the organs of the female, stuck obliquely into her side, and justifying the name "two-headed worm" which has been given to this wretched and duplex animalculus. The female bonellie is a sea worm shaped like a sort of cornucopia sack fifteen centimetres in length: the male is represented by a minuscule filament of about one or two millimetres, that is to say about one-thousandth her size. Each female supports about twenty. These males live, first in the œsophagus, then descend into the oviduct where they impregnate the eggs. Only their very definite function clears them from the charge of being parasites; in fact they were long supposed to be parasites, while men sought vainly for the male of the prodigious bonellie. Side by side with males who are merely individualized sexual organs, one sees males who have lost nearly all organs save the male organ itself. Certain hermaphrodite cirripedes (mollusks attached by a peduncle [stalk]) cling as parasites to the coat of other cirripedes: whence a diminution of volume, a regression of ovaries, abolition of nutritive functions; the stalk takes root in the living, nourishing milieu. But one organ, the male one, persists in these diminished cirripedes, and takes on enormous proportions, absorbing the whole of the animal. With only a slight further change one would see the transformation of male into male organ completely accomplished, as one does, moreover, in the hydraria. Become again an integral part of an organism from which it had formerly separated to become an individual, the male merely returns, to its origins and clearly certifies what they were.