DEGRADATION OF ORGANISATION 91 



morphosis ; and as they never launch themselves into the air, it is 

 very probable that their tracheae do not generally extend through- 

 out all parts of their bodies. 



INSECTS. 



Animals which undergo metamorphoses, and have in the perfecf state 

 two eyes and two antennae in their head, six jointed legs and wo 

 tracheae which extend throughout their body. 



As we continue to follow the inverse order from that of nature, 

 the insects necessarily succeed the arachnids. They constitute that 

 immense series of imperfect animals which have no arteries or veins ; 

 which breathe by air-carrying tracheae not limited to special parts ; 

 lastly, which are born in a state less perfect than that in which they 

 reproduce ; and which consequently undergo metamorphoses. 



In their perfect state all insects without exception have six jointed 

 legs, two antennae and two eyes in their head, and most of them 

 also have wings. 



The insects necessarily occupy the tenth rank of the animal kingdom 

 in the order that we are following ; for they are inferior to the arachnids 

 in perfection of organisation since they are not born like these latter in 

 their perfect state, and they only procreate once in the course of their 

 hfe. It is particularly in the insects that we begin to observe that the 

 organs essential to maintenance of life are almost equally distributed, 

 and in most cases situated throughout their bodies instead of being 

 isolated in special places, as is the case in the most perfect animals. 

 The exceptions to this rule gradually disappear, so that it becomes 

 ever more striking in the lower classes of animals. 



Nowhere hitherto has the general degradation of organisation 

 been more manifest than in the insects, whose organisation is less 

 perfect than that of the animals of any of the preceding classes. 

 This degradation comes out even within the various orders into which 

 insects are naturally divided ; for those of the three first orders 

 (Coleoptera, Orthoptera, Neuroptera) have mandibles and maxillae 

 in their mouths ; those of the fourth order (Hymenoptera) begin to 

 possess a sort of proboscis ; finally, those of the four last orders (Lepi- 

 doptera, Hemiptera, Diptera and Aptera) have really nothing more 

 than a proboscis. Now paired maxillae are nowhere found again 

 in the animal kingdom, after the insects of the three first orders. 

 With regard to wings, the insects of the six first orders have four, 

 all of which or only two serve for flight. Those of the seventh and 

 eighth have only two wings or else they are quite aborted. The 



