rate from one another, but connected by a lateral membrane, and each segment is furnished 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 vegetative portion of each subsegment is, moreover, developed much more highly than the ventral 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 Chilopoda shows that as the scale is descended the number of segments increases, the rudiments 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 appearance 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
