6 
INTRODUCTION. 
part of the cephalo-thorax, constitutes the brain, and sends forward nerves to the eyes and 
falces. The narrow oesophagus is inclosed by a short and thick collar, which expands into a 
large thoracic ganglion, having small, conoid projections at its sides, from whose apices 
nerves are distributed to the legs and palpi; and a double, longitudinal, nervous chord, 
extending from the thoracic ganglion into the abdomen, has its extremity dilated, and from this 
enlargement a great number of nerves pass off to the organs contained in the abdominal cavity. 
Comprised within the cephalo-thorax, to whose integuments they are firmly attached, are 
the muscles which give motion to the legs, falces, maxillae, and palpi. 
Nothing is known with certainty concerning the organs of smell and hearing in spiders. 
As regards taste, the choice which these animals make of their food sufficiently indicates that 
it exists, and it is probable that the organ is situated at the entrance of the pharynx. 
Numerous circumstances tend to prove that spiders are endowed with considerable delicacy 
of touch, but the instruments more especially adapted to bring them into relation with 
surrounding objects are the legs and palpi. The presence of eyes, which are of the kind 
termed simple, in opposition to those of insects and crustaceous animals, which are denominated 
compound, leaves no doubt relative to the sight of spiders, though, in all probability, they see 
objects distinctly at short distances only. 
When spiders are about to deposit their eggs they usually spin silken cocoons for their 
reception, which exhibit much diversity of form, colour, and consistency, and are placed in 
various situations, according to the economy of the species by which they are fabricated. 
Many spiders abandon their cocoons so soon as they are completed ; others manifest great 
attachment to them, watching over them with the utmost solicitude; and some, connecting 
them with the spinners by silken lines, or grasping them with the falces and palpi, transport 
them wherever they move. In numerous instances the eggs are agglutinated together into a 
compact mass ; in others they are united by filaments of silk ; and not unfrequently they are 
entirely free or unconnected. Their figure is either spherical, or somewhat elliptical; and 
their predominant colours are yellowish-white, yellow, orange-yellow, brown, and pink. 
Several sets of prolific eggs are frequently laid in succession, an interval of many months 
occasionally intervening between the extramission of two consecutive sets, by females which 
have not associated with males of their species after they have deposited the first set; but 
eggs produced without sexual intercourse are always sterile. For a knowledge of the various 
changes which take place in the ova of spiders previously to the extrusion of the young we 
are indebted to M. Herold, 1 whose highly interesting and important observations may be 
consulted with advantage by physiologists. The exterior covering of the egg consists of a very 
delicate membrane, in whose composition no pore or fibre has been perceived. Within this 
membrane there is a liquid in which several essential parts may be distinguished corresponding 
to the vitellus, the albumen, and the cicatricula in the eggs of birds. 
On the disengagement of young spiders from the egg, every part is enclosed in a 
membraneous envelope; they are embarrassed in their movements, are unable to spin or to 
seize their prey, and seem to be indisposed to action. For the unrestrained exercise of these 
functions it is requisite that they should extricate themselves from the covering which impedes 
them ; and this operation, or, as it may be termed, their first moult, occurs after a period 
1 * De Generatione Aranearum in ovo,’ folio, Marburg, 1824. 
