446 



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 

 ]\}f' -''' ganglion. These lateral masses 



give off nerves to the appendages. 

 From the back of the transverse 

 --th.g portion proceed three nerves. 

 Tlie 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 



Fig. 232.-Nervous and respiratory systems ^il^^tCS into a ganglion which 

 of a Phalangid. Nerves black, tracheae supplies the external part of 



white, c.gr, Cerebral ganglion; y', gr",*/", ,-, ,. rpi 



ganglia supplying viscera ; m.m, median ^"^ generative Organ. InC 



abdominal nerve ; oe, passage for oeso- inner branch, which is longer, 



phagus ; s^, stigma ; ^/t.^r, thoracic gang- i p i- ji 



lion ; tr, main truui; 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 



