TYPE TRACER AT A. 



485 



FIG. 223. ANTERIOR POR- 

 TION OF A CHILOPOD. 



at = antennas. 

 mx } = maxilla. 

 ms? second maxilla. 

 mxp maxilliped. 



clawlike and is perforated by the duct of a poison-gland. 

 Each trunk-segment, of which there may be over a hundred, 

 bears but a single pair of appendages, 

 there being no compound segments as 

 in the Diplopoda. Each leg is as a 

 rule seven-jointed, the coxal joints of 

 those of the same segment being widely 

 separated, and there is no modifica- 

 tion of the seventh pair to serve as 

 copulatory organs, though the pair of 

 the penultimate segment are much 

 reduced in size and lie at the sides of 

 the reproductive orifice. 



Stigmata are usually wanting in the 

 first three trunk-segments, but occur in 

 a certain number of the others, lying 

 usually laterally between the segments 

 except in Scutigera, in which they have a dorsal position. 

 They open into branched tracheal trunks which usually an- 

 astomose with one another, though in Scutigera they open 

 into sacs from which a large number of simple unbranched 

 tracheal tubes arise arranged in a bunch as in the Diplopoda. 

 Crural glands occur on the coxal joints of several of the 

 posterior appendages. 



The nervous system is arranged as in other Myriapods, and 

 simple eyes are usually present, in Scutigera only being closely 

 aggregated together to form a faceted eye. This, however, is 

 not a compound eye exactly similar to that of the Insects, but 

 is to be regarded simply as a close aggregation of simple 

 eyes. 



The reproductive organs are usually paired, and the sexes 

 separate. The ducts unite before opening to the exterior, so 

 that there is but a single opening situated on the antepenulti- 

 mate segment of the trunk, the appendages of which are 

 greatly reduced in size. The embryos of Scolopendra and 

 Geopliilus leave the egg with almost the same number of ap- 

 pendages as the adult, while those of Scutigera and LitJiobius 

 possess but seven pairs of legs (in addition to the maxillipeds) 

 and gradually acquire others by successive moults. 



