CLASSIFICATION OF CRUSTACEA. 1401 



The degradation pointed out, is hence, not merely a variation in 

 the position and size of certain organs, but an actual deterioration in 

 rank and intelligence. 



Other minor points exhibiting difference of grade, might be men- 

 tioned : but they have already been subjects of remark. We state 

 here only one — the character of the fingers of the large hands. In 

 the higher species, these fingers are pointed ; in a grade below, in 

 some groups, they have a spoon-like extremity. This excavate form 

 is often more perfect in young individuals than in adults, which is 

 one evidence that it is in fact proof of inferiority. By this mark we 

 learn that the Chlorodince are of lower grade than the Xanthines; the 

 Paguri, than the BernliarcU; the Mithracidw, than the Maiaclce, etc. 



Let us pass now to the Macroura. In the typical Macroural species, 

 the antennae, instead of being minute, with the inner retractile, are 

 long exsert organs, and the outer have a large plate as an appendage 

 at base ; the eyes are without sockets ; the outer maxillipeds are pedi- 

 form, and do not closely cover the other mouth organs; the abdomen 

 is often longer than the rest of the body, and has its six regular pairs 

 of appendages. All these points show a still further relaxing of the 

 centralization or cephalization of the species. There is an elongation 

 of the parts anterior to the mouth, and also of those posterior, and 

 this elongation of the two extremities is approximately proportional 

 to the relative dimensions of the corresponding parts in the Brachyura. 

 If we were to draw out an ovoid with the relative length and breadth 

 of a Macroural cephalothorax, and place its focus so as to correspond 

 with the position of the posterior margin of the epistome, in a manner 

 like that proposed for the Maia among Brachyura, the ovoid would 

 be very narrow, and the focus or centre proportionally farther from 

 the front than in the Brachyura. 



In following down the degradation of the Brachyura to the Ano- 

 moura, we have found the posterior legs becoming abbreviated, and 

 the whole structure in its aspect imperfect. But, in the typical Ma- 

 croura, there is nothing of this seeming imperfection. The legs are 

 all fully formed ; the animals are exceedingly quick in their motion, 

 instead of being sluggish ; and every organ is apparently in its most 

 perfect state for the uses of the system to which it is tributary. We 

 should, therefore, understand, that the process of degradation, alluded 

 to above, is not one actually passed through in the system of creation ; 



351 



