LAMARCK. 531 



ber, is one of such high consideration that it might be taken 

 as the distinction of the highest order, were it not that 

 Lamarck again fixes on still more influential organs fol- 

 lower divisions, viz., the respiratory organs, and their fitness 

 for aqueous or aerial respiration. The form of the columella, 

 the length of the siphonal canal, the shape of the right lip 

 of the aperture, the depth of the emargination, &c, furnish 

 him with good characters for the families. 



The Cephalopods, in this new arrangement, have three 

 primary sections, — the multilocular, the unilocular, and the 

 naked. This is the same as they were in 1809 ; but the 

 Carinaria was properly withdrawn from the unilocular cepha- 

 lopods, and in place of five there were now established nine 

 families, and a greater number of genera. These reforms 

 were made principally in the microscopic chambered shells, 

 which, we now know, are not molluscan ; but Lamarck 

 benefited Conchology by distinctly isolating the family 

 Ammonites, which he characterized and separated from those 

 Cephalopods that have the Nautilus for their representative. 



As Lamarck, in his subsequent publications, retained the 

 principles and main features of his system of 1812, it will 

 be most convenient to present it to you in this place with 

 his last improvements, as these are detailed in his " Histoire 

 Naturelle des Animaux sans Vertebres,"* — a great work 

 indispensable to every naturalist, and which must be daily 

 in your hands. I know of no other that can be compared 

 with it in point of utility to the practical conchologist, nor of 

 any other that has had a more salutary influence over the 

 progress of his study. 



Starting from the assumed principle that animal existences 

 have proceeded from a common origin, — the lowest entity 

 in creation, — and that they have, self-willed, gradually com- 

 plicated and elevated their structure, a certain stage is 

 reached where disturbing forces operate to direct the crea- 

 tive energy into two distinct roads, each leading upwards to 

 comparative perfection. Infusory animalcules lead on, in 

 one road, to the polypes ; and these again directly to the 

 radiated classes; and, by a bye-path, to the acephalous naked 

 mollusca. The latter constitute a separate class, which La- 

 marck first of all denominated the Tunicata. They are not 

 polypes, yet still less are they mollusca, for many kinds of 

 articulated animals occupy the wide interval between them, 

 wherein nature tarried, as it were, with the ascidian orders, 

 seemingly uncertain as to her future course. The Tunicata 

 are non-sentient, the Mollusca are sentient or instinctive 



* Seven vol?. 8vo., Paris, 1816—22. 



M M 2 



