154 AFFINITIES AND GEOGRAPHICAL 



Myriapod.C 3 } Here, however, there may be more than one 

 line of passage ; for the two great families of the myriapods, 

 the Julidse and Scolopendridse, are diverse in character, the 

 former being vegetable feeders, the latter carnivorous, and it 

 appears as a rule in the genetic system, that true carnivores 

 are always apart. Confining our view to the Scolopendridae, 

 we see a remarkable continuity of character and habits 

 transmitted to them from the presumed marine ancestor, 

 (nereis,) allowing for the altered medium of existence. The 

 scolopendra is an animal furnished with powerful destructive 

 organs ; and, living under stones and the bark of trees, and in 

 fissures generally, it is his custom to wind insidiously along, 

 and dart upon any little animal which comes in his way. Of 

 the nereides, on the other hand, we are told that they 

 " usually live in the excavations of littoral rocks, in the hol- 

 lows of sponges, in the interstices of the radicles of thalas- 

 siophytes, under stones, and in general in all bodies which 

 present fissures more or less profound . . . They all ap- 

 pear to feed upon animal substances. . . M. Bosc tells us 

 they live upon polypi and small worms, on which they throw 

 themselves, by darting the anterior part of their body, which 

 they have first contracted." 



The next articulate class demanding attention is the Crus- 

 tacea, animals in which the annular sections are covered with 

 a calcareous shell, and provided with jointed limbs, the respi- 

 ratory apparatus being branchial ; all are aquatic, except 

 some of the higher genera, which occasionally adventure upon 

 the land. They are in two great groups, entomostraca and 

 malacostraca, the former being the simpler, and exclusively 

 marine. Emmerich considers the Trilobites which figure so 

 conspicuously in the early rocks, as between the two divi- 

 sions, but most nearly allied to the first ; whence it would 

 appear that the Crustacea which make so early an appearance 

 in the rock series, are humble animals, only preceded in their 

 own sub-kingdom by a group, which, from their slight forms, 

 might be ill-adapted for preservation in strata exposed after 

 deposition to a high temperature. The .geological history of 

 the Crustacea tallies in other points with their gradation. In 



