EXTERNAL ANATOMY OF INSECTS. 665 



pairs; Craspedosoma, Jifty ; Geophilus electricus at least 

 sixty; in lulus terrestris there are more than seventy; in 

 I. sabulosus nearly one hundred; in Lfuscus, 124; and in 

 /. maximus 1 34 pairs or 268 single legs. But with respect 

 to the Geophili, luli, &c, it is to be observed, that the 

 number of pairs varies in different individuals; and the 

 circumstance that has been before mentioned a , that these 

 animals keep acquiring legs in their progress to the per- 

 fect state, instead of losing them, renders it difficult to 

 ascertain what is the natural number of pairs in any 

 species. 



2. Kinds. Upon a former occasion I gave you a suffi- 

 ciently full account of the kinds of legs 3 , and I have also 

 assigned my reasons for giving a different denomina- 

 tion to the anterior legs under certain circumstances 5 ; I 

 shall not therefore enlarge further upon this head. 



3. Substance. The substance of the legs is generally 

 regulated more or less by that of the rest of the body, 

 only in soft-bodied insects they seem usually more firm 

 and unbending. Each joint is a tube, including the mov- 

 ing muscles, nerves, and air vessels. 



4. Articulation with the Trunk. M. Cuvier has ob- 

 served that the hip (coxa), which is the joint that unites 

 the leg with the body, rather inosculates, in its acetabu- 

 lum, than articulates in any precise manner ; but this 

 observation, though true of a great many, will not apply 

 universally, for the legs of Orthopterous insects, and of 

 most of the subsequent Orders, are suspended rather than 

 inosculating. Even in many Coleoptera a difference is ob- 

 servable in this respect. I have before mentioned that 



* Vol. II. p. 312, 363, 365. » See above, p. 546—. 



c Anatom. Compar, i. 453. 



