338 LAMARCK, HIS LIFE AND WORK 



(chapter vii.) is devoted to the understanding, its origin 

 and that of ideas. The following additions relative 

 to chapters vii. and viii. of the first part of this work 

 are from vol. ii., pp. 451-466. 



In the last of June, 1809, the menagerie of the 

 Museum of Natural History having received a Phoca 

 (Phoca vitulina), Lamarck, as he says, had the oppor- 

 tunity of observing its movements and habits. After 

 describing its habits in swimming and moving on 

 land and observing its relation to the clawed mam- 

 mals, he says his main object is to remark that the 

 seals do not have the hind legs arranged in the same 

 direction as the axis of their body, because these 

 animals are constrained to habitually use them to 

 form a caudal fin, closing and widening, by spreading 

 their digits, the paddle {palette) which results from 

 their union. 



" The morses, on the contrary, which are accus- 

 tomed to feed on grass near the shore, never use their 

 hind feet as a caudal fin ; but their feet are united 

 together with the tail, and cannot separate. Thus in 

 animals of similar origin we see a new proof of the 

 effect of habits on the form and structure of organs." 



He then turns to the flying mammals, such as the 

 flying squirrel {Sciurus volans, (srobates, petaurista, 

 sagitta, and volucclld), and then explains the origin 

 of their adaptation for flying leaps. 



" These animals, more modern than the seals, having 

 the habit of extending their limbs while leaping to form 

 a sort of parachute, can only make a very prolonged 

 leap when they glide down from a tree or spring only 

 a short distance from one tree to another. Now, by 

 frequent repetitions of such leaps, in the individuals 



