440 ARACHNIDA—PHALANGIDEA * CHAP, 
known to be glands for the manufacture of the odorous fluid 
which these animals can exude. 
The thoracic ganglion expands, on either side of the oeso- 
phagus, into a mass which extends nearly as far forward 
as the apex of the cerebral 
ganglion. These lateral masses 
give off nerves to the appendages. 
From the back of the transverse 
portion proceed three nerves. 
The median nerve passes above 
the generative organs, and soon 
branches into two nerves which 
presently swell out to form 
ganglia of considerable size, 
beyond which they soon join 
again and give off an anasto- 
mosing net-work of nerve-fibres. 
The lateral nerves immediately 
branch. The outer branch 
Fic. 232.—Nervous and respiratory systems dilates into a ganglion which 
of a Phalangid. Nerves black, tracheae supphes the external part of 
Ua 
white. c.g, Cerebral ganglion; y’, 9”, 9’, : E 
ganglia supplying viscera ; m.n, median the generative organ. Tes 
abdominal nerve ; oe, passage for oeso- jnner branch, which is longer, 
phagus ; s¢, stigma ; th.g, thoracic gang- ; = 
lion ; ¢7, main trunk of tracheae. also forms a ganglion the nerves 
from which are chiefly distri- 
buted to the under surface of the alimentary canal. 
The respiratory organs consist of two large tracheal tubes 
with numerous branches, having their external openings or 
“stigmata” near the base of the fourth pair of legs. The two 
main tubes are directed forwards, and are mainly concerned with 
supplying the largely developed muscles of the legs. The dis- 
tribution of branches to the abdomen is comparatively feeble. 
The particular arrangement of tubes in P. opilio, according to 
Tulk, may be seen in the accompanying figure. There are a 
pair of coxal glands, of excretory function, opening in the 
neighbourhood of the coxae of the third pair of legs. 
The Phalangidea are remarkable among Arachnids in the 
possession of large protrusible external organs of generation. 
The ovipositor of the female may be as long as the whole body 
of the animal, and the intromittent organ of the male is of 
