LAMARCK. 529 



In 1809 Lamarck published his " Philosophy of Zoology." 

 My estimate of the work is much below that of Deshayes, 

 but I agree with him in thinking that it had an influence in 

 directing the attention of zoologists to higher matters of spe- 

 culation, than was deemed by many of them to be within 

 their cognisance ; and it treated matters which were more 

 strictly so with a wider scope, and with a bold disrespect of 

 established opinion, more characteristic of the period than of 

 the individual. The work contains a new edition of his 

 classification of the Mollusca, which are made to stand at the 

 head of invertebrate animals ; rather, however, because this 

 position favoured Lamarck's hypothesis of organic develop- 

 ment, than because of the influence of Cuvier's anatomies. 

 The novelty in the method is his introduction of a section, 

 borrowed from the Botanists, which he called a family, a 

 very convenient, and indeed important, innovation which 

 has not since been departed from. In his disposition of the 

 Acephales there is nothing new to remark ; but he follows 

 Cuvier in dividing the Cephales into Pteropodes, Grastero- 

 podes, and Cephalopodes. Into the latter order he now also 

 unfortunately introduced the microscopic multilocular shells, 

 as well as the Carinaria and the Argonauta. But I need not 

 enter into any further analysis of this method, for, in 1812, 

 it was republished with considerable modifications, necessi- 

 tated by the discoveries which Peron and Lesueur had made 

 in the Australasian seas, and by the continued fructifying 

 labours of Cuvier. Lamarck introduced then into the testa- 

 ceous Acephales their ordinal divisions of Monomyaires and 

 Dimyaires ; and although, at a first glance, it may seem to be 

 of little consequence whether an animal is connected to its 

 shell by one or by two muscles, it is actually far otherwise, 

 the resulting organic modifications being felt not only in the 

 form and structure of the shell, but even in the nervous sys- 

 tem, and thence also in the economy of the mollusks. These 

 divisions have, therefore, never disappeared from conchologi- 

 cal systems, although some exceptions to their literal accu- 

 racy have been pointed out ; and the characters on which 

 they rest are happily of ready apprehension in general. The 

 secondary divisions of this class were now derived from the 

 presence or absence of a byssus, the equality or unequalness 

 of the valves, the position of the ligament, the form of the 

 hinge, and the variations in the locomotive organs. 



The cephalous Mollusca were divided into five sections, 

 viz., 1, the Pteropods ; 2, the Gasteropods ; 3, the Tracheli- 

 pods ; 4, the Cephalopods ; and 5, the Heteropods. The 

 third and the fifth were new ; and the latter was placed above 



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