ON THE ANATOMY OF THE ARANEIDEA, 159 
_ men is opened, a large quantity of adipose matter comes into view, which sup- 
ports and separates the different organs. In recent specimens this tissue is 
formed into lobules, which are again connected by fine cellular tissue into 
larger lobes (see Plate XVI. fig. 8) ; when, however, spiders have been kept for 
some time in spirit, the connecting tissue disappears, the lobules break up, 
and a mere unconnected granular mass remains. This reservoir of fat is a 
storehouse of nutriment, which enables spiders to bear very long abstinence ; 
and when they have been deprived of food for a long while, the abdomen 
becomes small and shriveled. This adipose matter was described by Cuvier 
and others as the liver. The chief organs which the abdomen contains are 
the ovaries (in the female), the intestinal canal, and the glands for the secre- 
tion of the silk. The ovaries, which shortly before the deposition of the eggs 
occupy a large portion of the cavity, are seated in the central and posterior 
part; the intestinal tube runs through it, in nearly a straight direction, from 
the base to the apex; and the sacs and tubes which elaborate the material 
for forming the webs, are placed in the lower, lateral, and anterior parts. I 
shall confine myself to the anatomy of the last-named structures, merely 
noticing with regard to one of the others, that I have generally observed the 
lower part of the intestinal canal to be filled with a whitish turbid excre- 
mentitious fluid, sometimes mixed with black particles*. After having been 
some time in spirit, this fluid is converted into a whitish substance of the 
consistence of mortar. 
The silk-glands, with their excretory tubes, which I shall now proceed to 
describe in detail, are very numerous, and of very beautiful construction. 
They essentially consist of a number of hollow cavities or sacs, of different 
sizes and shapes, each of which is furnished with a distinct duct. None of 
them or their ducts have any communication with each other, but terminate 
separately at the extremities of the spinnerets. The nature and construction 
of the glands are essentially similar in all the species of British and foreign 
spiders that I have dissected, though they differ greatly in form and number. 
As might be expected, they are most highly developed in the web-spinning 
species; while in those that hunt for their prey, as the Lycose, they are few 
and small in comparison, with the exception of those species which are aéro- 
nautic in their young state. They appear to be similar in the males and 
females. 
When the integument of the lower and front part of the abdomen is re- 
moved, together with a thin layer of fat, and the muscles which move the 
spinnerets, a large bunch of minute vesicles (just visible to the naked eye in 
a large spider, such as Epéira diadema) is brought into view; these, exa- 
mined by the microscope, are found to be small transparent oval sacs about 
200th of an inch in diameter in Ap. diadema, with fine and exceedingly 
elastic ducts, which proceed in bundles into the anterior and posterior pairs 
of spinnerets ; few, if any, terminating in the intermediate pair. When accu- 
rately examined, these small glands are found to be of two kinds; the most 
superficial, which are fewer in number than the others in Ep. diadema, are 
spindle-shaped, and imbedded in oval capsules of an opake finely granular 
substance, which is brittle and easily rubbed off, when pressed between two 
pieces of glass. I have endeavoured to represent these in Plate XVI. fig. 10 a, 
and fig.11. The other cells, which are more deeply seated, are exceedingly 
numerous in some species; they are nearly transparent, but when examined 
by a good glass-look as if they were embossed, or covered with little eleva- 
» * Mr. Blackwall noticed that the excrement of spiders often contained these black par- 
ticles, which had previously been described as calculi, 
