31^ 



LAMARCK, HIS LIFE AND WORK 



its feet when it wishes to strike the water and propel 

 itself along its surface. The skin which unites these 

 digits at their base, by these acts of spreading apart 

 being unceasingly repeated contracts the habit of 

 extending ; so that after a while the broad membranes 

 which connect the digits of ducks, geese, etc., are 

 formed as we see them. The same efforts made in 

 swimming — i.e., in pushing back the water, in order 

 to advance and to move in this liquid — have likewise 

 extended the membrane situated between the digits 

 of the frogs, the sea-turtles, the otter, beaver, etc. 



" On the contrary, the bird whose mode of life 

 habituates it to perch on trees, and which is born of 

 individuals who have all contracted this habit, has 

 necessarily the digits of the feet longer and shaped 

 in another way than those of the aquatic animals 

 which I have just mentioned. Its claws, after a while, 

 became elongated, pointed, and curved or hook-like in 

 order to grasp the branches on which the animal often 

 rests. 



" Likewise we see that the shore bird, which is not 

 inclined to swim, and which moreover has need of 

 approaching the edge of the water to find there its 

 prey, is in continual danger of sinking in the mud. 

 Now, this bird, wishing to act so that its body shall 

 not fall into the water, makes every effort to extend 

 and elongate its legs. It results from this that the 

 long-continued habit that this bird and the others of 

 its race contract, of extending and continually elongat- 

 ing their legs, is the cause of the individuals of this 

 race being raised as if on stilts, having gradually 

 acquired long, naked legs, which are denuded of 

 feathers up to the thighs and often above them 

 (Systime des Animaux sans VerMres, p. 1 6). 



" We also perceive that the same bird, wishing to 

 catch fish without wetting its body, is obliged to 

 make continual efforts to lengthen its neck. Now, 

 the results of these habitual efforts in this individual 



