236 ANNULATA. 
ducts of a large digestive gland and then is continued 
as the vectum into the cloacal sac. The spider kills 
its prey by its poison cheliceree, bites it open with the 
cutting bases of the pedipalpi, and sucks its juices by 
means of its sucking stomach, The juices are stored in 
the stomach and its czeca and digested and absorbed in 
the intestine. We may note the absence of any crushing 
gastric mill, so characteristic of the lobster and cockroach, 
Again, we can observe a certain resemblance in the ali- 
mentary system of the spider to that of the leech, due to a 
similar method of feeding. 
The muscular system is much broken up into limb 
muscles and other special muscles, and it is 
difficult to recognise much trace of the annelid 
and protracheate arrangement. 
The coelom has much the same relationship as in the 
Jnsecta—that is, it is inferred that the perivisceral part is 
not represented. There is a pair of small and 
degenerate coxal glands which in some young 
spiders open by a duct at the bases of the legs. These 
are held to be vestigial excretory organs of the nephridial 
type, and in the young scorpion they are said to have 
internal openings into the ccelom. 
The heart is a long dorsal tube surrounded by a fer- 
cardial sinus into which it opens by three pairs of ostia. 
The heart is continued forward into main arteries which 
finally open into the venous sinuses composing the body- 
cavity. Some of these communicate with the pulmonary 
sacs and thence pass to the heart. The pulmonary sacs are 
therefore in the same position in the blood circuit as are 
the gills of the lobster and similarly the heart is systemic. 
The nervous system is concentrated in the cephalo- 
thorax. It consists of a brain above the pharynx, supplying 
the eyes and the chelicerz, and connected by a nerve-ring 
with a ventral nerve-mass formed of at least 
five pairs of fused ganglia. From it nerves are 
given off to the pedipalpi, the legs and the abdominal 
organs. pera shows a great degree of nerve-concentra- 
tion and in this respect differs from some Arachnida. 
The vestigial excretory organs, or coxal glands, have 
already been alluded to. The functional organs are four 
Muscular. 
Coelom. 
Nervous. 
