410 ON THE ORDERS 



read before the Physical Society of Geneva in 1805, and 

 in which M. Jurine has explained the analogy which 

 these organs bear to the wings of birds, a subject of late 

 still more rigorously and almost mathematically investi- 

 gated by M . Chabrier. 



It is obvious, nevertheless, that such a basis for a the- 

 ory is sufficiently flimsy, and would scarcely deserve much 

 attention, were not the theory itself susceptible of many 

 happy applications to fact. But as this is one of the great 

 tests of the worth of any new opinion, and is only inferior 

 to a sound deduction of it from actual experiment, I shall 

 now indicate the use to which M. Latreille's theory may 

 be converted. 



Boas Johansson, in the Amainitates Academics, sum- 

 med up the character of Annulose animals in these words : 

 " Htscce denique, ad umim omnia, animalia suis vestita os- 

 sibus cataphracta et quasi loricata, mirijice incedunt;" and 

 the foundation of M. Latreille's theory may be said to 

 rest upon this fact, that the Annulosa ought to be con- 

 sidered as clothed in their bones. Arguing therefore from 

 the established truth of the skeleton of the Fertebrata be- 

 ing referable to one model, he conceives that the Annu- 

 lose type may be discovered by a strict attention to the 

 segments which compose the external envelope of such 

 ^iiimals. 



The body of an Amphipod Crustaceous animal is, as 

 our author observes, formed of fifteen articulations, the 

 three first of which, having the manducatory organs at- 

 tached to them, constitute the head, the five following the 

 thorax, and the remaining seven the abdomen. In Deca- 

 pod Crustacea and the majority of the Arachnida, the 

 upper covering of the thorax is united to the head, form- 



