210 



ARACI-INIDA- 



but in some cases there exists a well-marked 

 character. The greater part of the aranese 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 these, 

 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, Tc- 

 genaria domestica. 



The male of this species, when arrived at the 

 adult state, presents a considerable dilatation at 

 the extremity of its maxillary palp (Jig. 100, ). 

 On carefully observing this swelling, it is per- 



Fig. 100. 



ceived to arise from the 

 penultimate joint (6), 

 which is enlarged and 

 spiny. The swelling it- 

 self, or what has been 

 termed penis, (Jig. 100 

 and Jig. 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. 



Fig, 101. In order that this 



part should be a 

 penis, as has been 

 supposed, and as 

 many naturalists 

 still believe,itought 

 to be perforated for 

 the emission of 

 the prolific liquor. 

 Now, Treviranus is 

 certain that it is not 

 perforated by any 

 foramen, and also that there does not exist in 

 the interior of the palp any excretory duct 



which could have brought to this part the secre- 

 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. 

 (Fig. 102, b } b.) These two organs open into 

 two long, slender, tortuous, 

 Fig. 102. 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- 

 c out doubt instantaneously ; 

 which explains why no ob- 

 server has hitherto witness- 

 ed the act.* 



The remarkable sexual 

 differences which obtain in 

 a the araneae 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, (jig. 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 



* Mr. Blackwall denies the accuracy of Trevi- 

 ranus's opinion, and supports that of Lister and the 

 older observers, as to the sexual function of the 

 maxillary palp, founding his remarks on observa- 

 tions made on various individuals of the genera, 

 Epeira, Theridion, and Agelena. We must refer 

 for the details to the memoir before quoted from the 

 Transactions of the Linnaean Society. ED. 



