192 T'ransactions.— Zoology. 
generally as a single one united throughout its whole length, and occupying a 
transverse position in front of the rest. It is but lately that spiders have 
been observed with two spinners only (“Spiders of Palestine and Syria,” by 
O. P. Cambridge, Proc. Zool. Soc, 1872, p. 260; also, An. N. H., 1870, 
pp. 414—417, ibid.) 
The spinners vary greatly in size and structure, as well as in number, but 
hitherto their use in classification has not been what one might have expected 
from so essential and important a portion of structure. The fourth pair of 
spinners, when present— which it is in both sexes is correlated, but only in 
the female sex, with the peculiar double series of closely-set curved bristles 
(mentioned above) on the metatarsi of the fourth pair of legs. Mr. Blackwall 
has given the appropriate name of calamistrum to this series of bristles, and 
has proved that their function is to card or tease a peculiar kind of adhesive 
silk secreted and emitted from the fourth pair of spinners—the use of the 
silk is for disposal about the spider’s snare, rendering the entanglement of its 
prey the more speedy and certain. Immediately above the spinners is a small 
nipple-like prominence, of greater or less size, which indicates the orifice of the 
anus (f. 15р). 
As it does not enter into the design of this short introduction to go into 
the anatomical details of the Araneidea, it remains only to touch briefly upon 
their distribution and habits, and to make a few observations on their capture 
and mode of preservation. 
It should, however, be noticed here that the sexes of spiders, though not 
generally presenting any great difference in size, yet in very many cases show 
it to an extreme extent. The male is nearly always the smallest, though its 
legs are often much the longest, but with many of the Epeirides and Thomisides 
the male is scarcely more than an eighth or a tenth of the length of the 
female. This is a fact to be borne in mind, otherwise the male of many such 
spiders will be overlooked, or thought to be of a different species, while, if it 
is remembered, the collector may often have an opportunity of noting import- 
ant circumstances in the economy of spiders which at first sight may seem to 
be unconnected with each other ; and thus spiders now perhaps described as 
totally different species may be found to be the different sexes of the same. 
In determining the species of spiders it is very convenient to obtain 
comparative dimensions from different portions of structure ; thus the position 
of the eyes on the fore part of the caput furnishes us with the facial space 
(f. 5e, and 19а), and the clypeus (f. 3n, and 196). The comparative extent of 
