222 Mr. BlacR wall 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 papillæ 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 papillæ connected with the inferior spinners of 
Drassus cupreus, 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 papillz on the spinning mammule 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 papillz on the terminal joint of the superior spinners of 
Walckenaera 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 papillæ, 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 labyrinthica, Tex- 
trix agilis, Drassus saxatilis, Blackw., and some other British species. This 
deviation from the prevailing structure has induced Lyonnet, Savigny, Trevi- 
