222 Mr. Blackwall on the Number and Structure of 



inferior spinner of Drassus ater, which can be wholly retracted within the 

 middle joint at the will of the spider, I subjected numerous individuals to a 

 strict scrutiny, when I was surprised to discover that the number varied with 

 the age of the animals. In specimens which had attained nearly a third of 

 their growth they usually amounted to five or six ; in others, which were about 

 two-thirds grown, to six or seven ; and in adults, which had acquired their 

 full complement, they were uniformly eight ; two of them, situated on the in- 

 ferior surface of the spinner, at a greater distance from its extremity than the 

 rest, being minute and almost contiguous. It is a fact deserving of notice, 

 that the papillae are not always developed simultaneously on these spinners, 

 six, seven, or eight being sometimes observed on one, when five, six, or seven 

 only are to be seen on the other ; and this remark is applicable, not to the 

 inferior spinners alone, but to the intermediate ones also, which, in mature 

 individuals, are further modified by having the extremities of the terminal 

 joints directed forwards at right angles to their bases. I have, in like man- 

 ner, ascertained that the papillae connected with the inferior spinners of 

 Drassus cujrreus, Blackw., and the superior spinners of Segestria senoculata, 

 follow the same law of development ; but whether it does or does not hold 

 good with the papillae on the spinning mammuiae of spiders in general, I am 

 not at present prepared to decide ; yet, could I rely on analogy, and on the 

 results of observations, too limited and imperfect to command implicit con- 

 fidence, I should be disposed to answer affirmatively. The inquiry, however, 

 to which I am solicitous to direct the attention of arachnologists, is one of 

 considerable interest. 



In addition to the papillae on the terminal joint of the superior spinners of 

 If^alckenaera acuminata, a large one, much dilated at its base, occurs near the 

 extremity of their middle joint, on the inner surface. 



The superior and inferior spinners of many spiders are triarticulate ; and 

 when the terminal joint of the former is greatly 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 Tegenaria domestica, Tegenaria civilis, Agelena labyr'mthica, Tex- 

 trix agilis, Drassus saxatilis, Blackw., and some other British species. This 

 deviation from the prevailing structure has induced Lyonnet, Savigny, Trevi- 



