STRUCTURE, FUNCTIONS AND OiCONOMY OF ARANEIDEA. G5 



in adults of either of these or the preceding species, j'et the two minute ones 

 belonging to each mammula are present invariably *. 



The superior spinners of many spiders are triarticulate ; and when the 

 terminal joint is considerably elongated, thickly clothed with hairs, and tapers 

 to a point, the papillae, in the form of hair-like tubes dilated at the base, are 

 commonly distributed along its inferior surface, as in the case of Agelena 

 labyrinthica, Tegenaria domestica, and Textrix lycosina. This deviation from 

 the prevailing structure has induced Lyonnet, Savigny, Treviranus, Audouin, 

 and other skilful zootomists, who have failed to detect the papillae, to regard 

 the superior mammula, thus modified, as anal palpi, and to deny that they 

 perform the office of spinners ; but if these parts be carefully examined with 

 a powerful magnifier in living specimens during the exercise of tiieir function, 

 the fine lines of silk proceeding from the papillae cannot fail to be discerned, 

 and a correct knowledge of their external organization may thus be obtained. 

 Not being aware, apparently, of the publication of this discovery in the ' Re- 

 port of the Third Meeting of the British Association for the Advancement 

 of Science, held at Cambridge in 1833,' p. 4-45, Baron Walckenaer, in the 

 Supplement to the second volume of his ' Histoire Naturelle des Insectes 

 Apteres,' p. 407, has ascribed it to M. Duges, whose observations on the 

 subject in the ' Annales des Sciences Naturelles,' seconde serie, t. vi., Zoologie, 

 p. 166, were not published till 1836. 



One of the most striking peculiarities in the structure of the Ciniflonidce, 

 which serves to distinguish them from all other animals of the order Araneidea 

 at present known, is the possession of a fourth pair of spinners. These spinners 

 are shorter and further removed from the anus than the rest, being situated 

 at the base of the inferior intermediate pair, by which they are almost concealed 

 when in a state of repose. Their figure is somewhat conical, but compressed 

 and truncated, so that the base and apex are elliptical with long transverse 

 axes. Consisting of a single joint onlj'^, each is connected with the other 

 throughout its entire length, the extremity alone being densely covered M^ith 

 exceedingly minute papillae, which emit the viscous matter that is formed 

 by the calamistra into a delicate tortuous band constituting a portion of every 

 flocculus in the snares of these spiders, and chiefly imparting to them their 

 most important property, that of adhesionf. 



Arachnologists have not bestowed that degree of attention on the palpi of 

 spiders to which their diversified structure and importantfunctions undoubtedly 

 entitle tliem. 



Much difference is observable in the relative proportions of the several 

 joints of the palpi of female spiders, not only in species constituting the same 

 family, but even in those belonging to the same genus ; while, on the other 

 hand, it frequently happens that females belonging to diff"erent genera bear 

 a striking resemblance to each other in this particular. It is among male 

 spiders, however, that these peculiarities are the most marked, and to them 

 may be added structural differences and resemblances both of the palpi and 

 sexual organs still more conspicuous. 



A great similarity in the form of the organs of reproduction, in the simplicity 

 of their structure, and in the manner of their connexion with the digital joint 

 of the palpi, which has no cavity opening externally, may be seen in certain 

 males of the family Dysderidce ; in Dysdera erythrina, Dysdera hombergii, 

 Segestria perfida, Segestria senoculata, and Oonops pulcher, for example ; 

 and this similitude is extended to the males of various species belonging to 

 the family Mygalida. 



Between the males of Pachygnatha clerckii and Tetragnatha extensa there 

 * Transactions of the Linnaean Society, vol. xviii. p. 219-224. f Ibid. pp. 223, 224, 60G, 



1844. ^ F 



