ARACHNIDA. 



263 



accessory organs of this sex are quite distinct and remote from each 

 other ; the principle of such separation, which is exemplified in the 

 relation of the Fallopian tube to the ovarium in Mammalia, is carried 

 to an extreme in regard to the vesicula seminalis and testis in the 

 spiders. If the analogy of the female parts be here, as in other 

 animals, a guide in the determination of the essential organs of the 

 male, the testes ought to be the two long vermicular tubes, applied to 

 the under wall of the abdomen, which commence posteriorly, either 

 by a simple sac, as in the Mygale, or by an oblong vesicle, as in the 

 genus Pholcus, the ducts of both of which terminate anteriorly by 

 two approximate orifices, or else by a common opening, situated be- 

 tween the two pulmonary stigmata (y?^. 114. k). 



The second or copulatory part of the generative organs is confined 

 to the two last joints of the maxillary palp {Jig- 11 4. c, d) : the 

 1J4 ,,^,, dilatation of these joints is chiefly formed by a 

 membranous tube or sac, commencing at the pe- 

 nultimate and reaching its greatest expansion at 

 the last joint (d) : this tube appears to line a ca- 

 vity in the ordinary state ; but it can be distended, 

 everted, and erected ; when it is seen to be termi- 

 nated by a horny appendage. 



In the female spider the ovarium usually presents 

 the form of a simple elongated fusiform vesicle {fig- 

 113. o), closed at one extremit}^ and communicating 

 with a slender oviduct Qj) at the other, which duct, 

 after more or fewer convolutions, terminates at the 

 corresponding angle of the simple transverse vulva. 

 It is situated, like the outlets of the vasa deferentia, 

 between the pulmonary stigmata. Each ovarium is 

 divided in the Epeira, or diadem-spider, by a trans- 

 verse septum, and the eggs are laid at two distinct periods. 



The most careful observations, repeated by the most attentive and 

 experienced entomologists, have led to the conviction that the ova 

 are fertilised by the alternate introduction of the appendages of the 

 two palpi of the male. Treviranus's supposition that these acts are 

 merely preliminary stimuli, has received no confirmation, and is 

 rejected by Duges, Westwood, and Blackwall. At the same time, 

 the most minute and careful research has failed to detect any con- 

 tinuation of the vas deferens into the terminal erectile sac of the palp, 

 or any other termination than the abdominal opening above described. 

 Duges offers the very probable suggestion that the male himself may 

 apply the dilated cavities of the palpi to the abdominal aperture, and 

 receive from the vasa deferentia the fertilising fluid, preparatory to 



s 4 



Tegenaria domestica. 



