440 PHYSIOLOGY. 



former is more densely covered with hair, and more deeply coloured 

 than the latter does not at all suffice ; for, in the first place, in very 

 many insects, particularly in the beetles, the under side is that which 

 makes the greatest bow, and, therefore, the distending side, and often, as 

 in the bees, is the most densely haired, and besides the darker colouring, 

 as the consequence of a greater effect of light, is no proof in opposi- 

 tion. This is evinced by the universally brighter colour of the upper 

 side of the abdomen in the beetles, in which the elytra oppose the 

 effect of light. What also he cites in opposition from the situation and 

 posture of the extremities is also inapplicable ; for the extremities pro- 

 ceed precisely from the same side as they do in the vertebrata, namely, 

 from the dorsal side. In all the vertebrata the extremities are attached 

 to particular bones which stand in connexion with the vertebral column. 

 These bones are, for the anterior extremity, the scapulae, and for 

 the posterior one the ilium, of the pelvis. We refind these portions 

 of the skeleton also in the Arthrozoa, at least in the most perfect among 

 them, namely, the beetles; but they do not lie superficially attached 

 to the vertebrae and its arches, but as external cases they are con- 

 nected with the ring which is formed by the vertebra and its processes, 

 and necessarily at the spot where they properly belong, namely, between 

 the vertebra and the sternum. This approximation of the shoulder- 

 plate to the vertebral column is very distinct in the anterior extremity 

 of the vertebrata, it descending closely contiguous to the vertebrae ; in 

 the posterior extremity, however, where the ribs are wanting, it is 

 even traced, in as far as here the ilium borders immediately upon the 

 vertebral column, and when the sternum here, the os pubis is wanting, 

 it presents itself as an arched process, upon the vertebral series of the 

 pelvis. The same is the case in insects ; here also the ribs are compressed, 

 and the scapulae take their place. We, therefore, obtain in insects both 

 a shoulder-blade and a pelval piece ; the first is also the plate, called 

 by us the scapula, the latter our parapleura, the ischium of Straus, 

 which, properly, should be called the ilium. The most distinct proof 

 that these pieces merit their names is the fact that the muscles which 

 move the thighs, namely, its flexor, thence proceed, and that conse- 

 quently the femur is attached to these pieces. In the anterior legs it 

 is the omia which correspond with them in situation and function 

 Analogous to the dorsal and ventral plates these three plates might 

 therefore, be called the premium, mesomium, and metomium, whereas 

 the dorsal plates should now be called pro-, meso-, and metastcrmim 



