ANNULOSA : AEACHNIDA. 205 



the appendages of the two palpi of the male. Treviranus's 

 supposition that these acts are merely preliminary stimuli, has 



Fig. 59. Araneida. TJieridion riparium, male and female, enlarged. 



received no confirmation, and is rejected by Duges, Westwood, 

 and Blackwall ; and with good reason, as the detection of the 

 spermatozoa in the palpal vesicles has shown. . . . Duges 

 offers the very probable suggestion that the male himself may 

 apply the dilated cavities of the palpi to the abdominal aper- 

 ture (of the testes), and receive from the vasa deferentia the 

 fertilising fluid, preparatory to the union. . . Certain it is 

 that an explanation of this singular condition of the male ap- 

 paratus, in which the intromittent organ is transferred to the 

 remote and out- stretched palp, is afforded by the insatiable 

 proneness to slay and devour in the females of these most 

 predaceous of articulated animals.' (Owen.) 



The Spiders are oviparous, and the young pass through no 

 metamorphosis ; but they cast their skins, or moult, repeatedly, 

 before they attain the size of the adult. 



DISTRIBUTION OF ARACHNIDA IN TIME. The Araclmida are 

 only very rarely found in a fossil condition. As far as is yet 

 known, both the Scorpions and the true Spiders appear to 

 have their commencement in the Carboniferous Epoch, the 



