204 ARACHNIDES. 



The abdomen is composed of twelve annuli, those of the tail included,' 

 the first is divided into two parts, of which the anterior bears the 

 sexual organs, and the other the two combs. These appendages are 

 composed of a principal, narrow, elongated and articulated piece, 

 movable at base, and furnished along its inner side with a suite of 

 little hollow laminae, united to it by an articulation, that are nar- 

 row, elongated, parallel, and similar to the teeth of a comb; their 

 number is more or less considerable according to the species; it 

 varies to a certain extent, and perhaps with age, in the same spe- 

 cies. No positive experiment has yet determined the use of these 

 appendages. The four following annuli have each a pair of pulmo- 

 nary sacs and stigmata. Directly after the sixth, the abdomen 

 becomes suddenly narrowed, and the remaining six, under the form 

 of joints, compose the tail. All the tarsi are alike, and consist of 

 three joints, with two hooks at the end of the last. The four last 

 legs have a common base, and the first joint of the hip is soldered; 

 the two last are even partly fixed against the abdomen. 



The two nervous cords, proceeding from the brain, unite at in- 

 tervals and form seven ganglions, the last of which belong to the 

 tail. In all other Arachnides, there are never more than three. 



The eight stigmata open into as many white bursae, each contain- 

 ing a great number of very slender, small laminae, between which 

 it is probable that the air passes. A muscular vessel extends along 

 the back, and communicates with each bursa by two branches(l); it 

 also distributes vessels to every part of the animal. The intestinal 

 canal is straight and slender. The liver is composed of four pairs 

 of glandular clusters, which pour their humour into the intestine 

 at four points. The male has two copulating organs arising 

 near the combs, and the female has two vulvae. The latter open into 

 a matrix consisting of several inter-communicating canals, which 

 in the proper period are found filled with living young ones; the 

 testes are also formed of some anastomosing vessels(2). 



These Arachnides inhabit the hot countries of both hemispheres, 

 live on the ground, conceal themselves under stones and other bo- 

 dies, most commonly in ruins, dark and cool places, and even in 

 houses. They run with considerable swiftness, curving their tail 

 over their back. They can turn it in every direction, and use it for 

 the purposes of attack and defence. With their forceps they seize 



(1) See our preceding remarks on the circulation of the Arachnides Pulmo- 

 narix. 



(2) For the anatomy of* the Scorpion, see Treviranus, Marcel de Serres, and 

 Leon Dufour, Journ. de Phys., June 181T. 



