THE MYRIAPODA OF NORTH AMERICA. 139 



rate from one another, but connected by a lateral membrane, and each segment is fur- 

 nished with a single pair of large legs. 



In the Diplopoda, one subsegment is not thus developed at the expense of the other, but, 

 the two coalescing, the perfected whole is obtained by their mutual growth. There are 

 therefore two sets of appendages, two pairs of legs, to each segment. The dorsal or vege- 

 tative portion of each subsegment is, moreover, developed much more highly than the ven- 

 tral or neural arc. Indeed, the scuta completely absorb the lateral membranes, and abut 

 directly against the sterna. These latter are always more or less atrophied, and, their 

 appendages partaking of their stunted growth, the legs are much smaller than in the 

 Chilopoda. The excess of the vegetative systems point to a position below the Chilopoda, 

 an indication which all the other minor facts corroborate. An examination of the Chilo- 

 poda shows that as the scale is descended the number of segments increases, the rudi- 

 ments of the anterior subsegments become more and more pronounced, and the legs 

 smaller and smaller, thus approaching the diplopod type. 



In the Diplopoda the genital apertures are placed in the anterior portion of the body, 

 and, as far as I have examined, always furnished with more or less prominent organs ; 

 whilst in the Chilopoda they are placed in the posterior portion of the body, and very 

 generally not so provided. There is also a great and persistent difference in the appear- 

 ance of the anal aperture in the two orders. 



The whole organization of the Chilopods fits them for their predatory and carnivorous 

 habits. The distinctness of the segments, which are not closely approximated, but are 

 conjoined by membranes, and the flexibility of the segments themselves, enable them 

 to move their bodies in every conceivable direction. Their highly organized muscular 

 and nervous systems, the compactness of their intestinal apparatus, and the length and 

 power of their legs, all betoken habits of great activity. Whilst the formidable nature of 

 their mandibles, and the sharp spines, both lateral and terminal, with which their feet are 

 armed, fit them for predatory warfare. 



There can be no doubt but that they are provided with poison glands situated at the 

 base of the mandibular teeth, and perhaps also at the bases of the terminal claws of the 

 feet. I remember once to have been bitten by a female Scolopocryptops sexspinosa, who 

 was trying to defend her young. Though of such insignificant size, when compared with 

 the tropical Scolopendra, yet the pain produced lasted for several hours. It is therefore 

 easily to be imagined that the huge species, a foot in length and inch in breadth, found in 

 the tropics, have the power of doing considerable mischief. I have been informed by a 

 resident of Texas, that minute ulcers follow the wounds made by the feet of S. heros on 

 the skin. 



The Diplopods depend upon the vegetable kingdom for their sustenance. The body is 



