Dr. J. Young on the Malacostraca of Aristotle. 243 



a remarkable generalization, far in advance of the time. On 

 what is it based ? Articulation, which makes both these sub- 

 classes members of a wider natural class, was not recognized by 

 Aristotle. Their separation is based upon the extraordinary 

 ground that, while in the former the hard and soft part3 are 

 distinct, in the Insecta the body is of a uniform hardness, 

 "more fleshy than bone, more bony and earthy than flesh." (De 

 Part. ii. 8.) 



The above group-names are all adjectives, and, as Sundevall 

 suggests in the case of the second, are definitions rather than 

 names. Scleroderma is sometimes used for Malacostraca : the 

 meaning seems identical ; at least no passage suggests any gra- 

 dation of hardness as implied in the different terms. They are 

 probably all the invention of Aristotle, who several times alludes 

 to the want of single terms to include large groups. It is 

 scarcely necessary to remark that yevos and eJSo? have in Aris- 

 totle no fixed meaning ; they are with him, as with naturalists 

 prior to Linnseus and with most men still in ordinary talk, con- 

 vertible terms, for which kind is the best English equivalent. 



The yevt] /jbiyiara included under Malacostraca are Astacus, 

 Carabus, Caris, and Carcinus. They are all Decapoda, the last 

 belonging to the section Brachyura, the first three to that of 

 Macrura. In arranging the anatomical and physiological de- 

 tails scattered through the several treatises, I have followed 

 convenience, not Aristotle, and grouped them under the usual 

 systematic heads. In the text, the position, not the function, 

 of organs determines the order in which they are mentioned. 

 The gain in clearness is counterbalanced by the necessary neg- 

 lect, in this arrangement, of the interesting view we might 

 otherwise have of the author's modified opinion in successive 

 works. The references will be sufficient, it is hoped, for the 

 reader to follow these changes when they occur. 



Tegumentary system. — The external covering is flexile, not 

 brittle. The earthy part is external, so as to form a kind of 

 "kitchen" for the better conservation of such heat as is generated; 

 for these animals, being bloodless, are of a cold nature : it is also 

 a protection to the soft parts (De Part. ii. 8). The cause of its 

 hardness is curious : skin is the result of evaporation by internal 

 heat, the viscid material (to yXLa^pov) parting with its moisture; 

 it is, therefore, not merely because it is on the surface that this 

 solidification takes place. The hardness of the shells in Mala- 

 costraca and Ostracoderma is due to the dryness of the viscid 

 material in them (De Gen. ii. 6); for their heat is insufficient to 

 cause evaporation. The important part assigned to heat in the 

 animal economy, or at least in the speculations of ancient philo- 

 sophers regarding it, is a necessary result of their ignorance of 



16* 



