Internally there exists in the abdo men of spiders a special secretory ap paratus, which con sists of intestiniform canals, united toge ther, and variable in number and extent according to the species. In Clu bione atrox, they consist, according to Treviranus, of four vessels, two large (fig. 99, a a) and two small (b b); near their base, and not far from the point where they open into the spinnarets, a number of small supplementary canals (c c) may be observed. ( Fig. 96 represents the spin narets in the same species.) Generative system.—In the arachnidans the sexes are placed, as in insects, in different in dividuals. It is not always an easy matter to distinguish outwardly the male from the female ; but in some cases there exists a well-marked character. The greater part of the araneze of the male sex have, at the extremity of their maxillary palp, a swelling containing a compli cated structure, which is not found in the female. Until lately this protuberance was considered, notwithstanding its anomalous po sition, as the penis of the male; and even now this opinion is maintained by many naturalists. All observers indeed, both ancient and mo dern, agree in stating that copulation takes place by means of this part. They have repeatedly observed the fact, and have described the pro cess with all the details that can inspire con fidence in their observations. Nevertheless it appears to us certain, if the anatomical facts we are about to disclose are accurate, that there is some mistake on their part, and that what they have taken for the act of copulation was in reality only a prelude to it. It is indeed true that the male spiders are distinguished from the females by the swelling at the extre mity of the maxillary palp, and that that swel ling presents a very complicated structure. Treviranus, Savigny, and, earlier than Ahese, Lyonnet, have given detailed figures of it, which may be consulted with advantage: our descrip tion will be after that of Treviranus, and from observations made on the common spider, 're genaria domestica.
The male of this species, when arrived at the adult state, presents a considerable dilatation at the extremity of its maxillary palp (fig.100, a).
On carefully observing this swelling, it is per ceived to arise from the penultimate joint (b), which is enlarged and spiny. The swelling it self, or what has been termed penis, (fig. 100 and fig.101, a,) is a con-. cave body from which a membranous, vesi cular, and glandiform body (c) protrudes, ter minated by several horny pieces (d), which are curved and pro ject but slightly in this species, but ac quire, in others, a con siderable development, and protrude in the form of long hooks having a much greater complication of structure.
In order that this part should be s penis, as has beer supposed, and a: many naturalist: still believe, it ough to be perforated fa the emission o the prolific liquor Now, Treviranus certain that it is no perforated by an: foramen, and also that there does not exist ii the interior of the palp any excretory duc which could have brought to this part the tion of the testicles. Lastly, and this proof is
still more conclusive, on examining carefully the under surface of the abdomen of a male, he discovered at its base, i. e. at the point where it is inserted into the thorax, between the aper tures of respiration, and at the part correspond-. ing to the vulvary opening of the female, two very small orifices, placed in a transverse fissure, which he ascertained to be the true outlets of the male apparatus. He found in the inte rior of the abdomen two cylindrical dilated vessels, which he determined to be the testes.
hese two organs open into two long, slender, tortuous, excretory canals (c), which terminate at the two orifices of which we have spoken (a), but without the appear ance of any superaddition of a firm or horny part that can be compared to a penis. From this description it is certain that what has been regarded as the act of copu lation, has been only preli minary, and that the intro duction of the extremity of the maxillary palp of the male into the vaginal aper tures of the female was for the mere purpose of opening the oviducts in order that the ac tual coitus should be effect ed with facility and with out doubt instantaneously ; which explains why no ob server has hitherto witness ed the act.* The remarkable sexual differences which obtain in the araneoe are not found in other arachnidans. Thus in the scorpions the maxil lary palps have a similar organization in both sexes, being terminated by pincers, both in the male and female, '(fig. 84, b.) The external aperture of the male apparatus is placed behind the thorax, and manifests itself by the presence of a valve formed by two semi circular pieces (fig. 84, c.) The internal struc ture of these organs is but imperfectly known. Treviranus believes that he could distinguish the testicles which terminated at the extremity in a kind of horny penis. Leon Dufour has given a more detailed description of these or gans, together with a figure which represents each testis, as being a large network of three meshes formed by cylindrical tubes.
The male, like the female scorpion, presents at the inferior part of the body on either side of the valve certain organs of a singular structure which are called combs, pectines, (fig. 84, d,) on account of the disposition of a series of small appendages of which they are formed, and which are arranged on the lower surface one beside the other, like the teeth of a comb. Many speculations have been offered respecting their uses. Many naturalists believe that they render some assistance in the act of impregna tion. Some suppose that they are extended during progression, and prevent the abdomen of the scorpion from trailing on the ground : others, again, regard them as hygrometrical organs, by means of which the animal judges of the humidity of the atmosphere. These are, however, all mere gratuitous hypotheses un supported by any observation ; and the fact is that we have yet to learn the use of these pec tinated appendages.