Bivalve Molluscous Animals, 198 



mud OP the rock which contains them. Hence it results that the artifi* 

 cial position assigned by Lamarck, differs completely from the natural 

 condition of bivalves, for it forms an angle of 90° with it j and that the 

 position adopted by M. Deshayes differs from the natural one by no less 

 than 180°, or, in short, precisely reverses the shell, by putting below 

 what in the normal state is above, just as if we were to place a man with 

 his feet in the air. As to the position adopted by M. de Blainville, it 

 approaches more to the ordinary condition of the shell, for, by inclining 

 it a quarter of a circle, we restore matters to their natural condition. 



Of all these artificial positions, the farthest removed from the truth id 

 that adopted by M. Deshayes. Its author supports it by saying, that 

 the mouth is situated at the extremity, which he places above, while the 

 anus is thus behind. If we were to follow a purely systematic course 

 with regard to the position of animals, without paying any attention to 

 their normal state, we should arrive'^at the most absurd consequences. 

 For example, is it necessary for us, because man in his usual position 

 has a vertebral column which follows a vertical line, and because he car- 

 ries his head at the upper extremity of that line, is it necessary, I say, 

 on this account to place the other mammifera in an analogous position ? 

 Certainly not, and no one, I believe, has yet thought of changing their 

 normal position, any more than of reversing an echinus by placing the 

 mouth upwards, and the anus downwards, — a position contrary to nature. 

 It is, in my opinion, necessary under all circumstances, to assign to 

 animals in the figures representing them, a position analogous to that 

 which they usually possessed in the different phases of their existence. 



Such considerations have induced me to investigate the reasons which 

 have given rise to the singular positions assigned to the mollusca, and' 

 the injurious consequences which may thus result to science. 



As I have remarked regarding the Gasteropodous mollusca, the special 

 study of shells, conchology, having for a long period been considered as a 

 separate branch of the science which treats of the molluscous animals form- 

 ing the most essential portions of these very shells, there has resulted an 

 erroneous manner of viewing them, to which, however, we have been 

 accustomed up to the present time. We may even assert that this fact 

 is so general, that, including museums, there are more than nine- tenths 

 of our collections which contain none of the animals, — a state of matters 

 which tends to perpetuate the fake direction given in the most recent 

 works, where not an animal is figured, and merely the calcareous cover- . 

 ings are represented. 



It has never been proposed to change the normal position of birds, or 

 of quadrupeds, because we see them everywhere, and the least observant 

 eye is accustomed to it. The natural position of a bivalve molluscous 

 animal is far from being so well known, for scientific men themselves 

 differ on the subject. Being in possession of numerous shells, and a few 

 animals, authors have fixed a position in their cabinets, either according 

 to the form of the shell itself» as is the case with Linneeus and Lamarck, 



