Bie 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—z.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 dogs, thelsea-turties, 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 
FESUs. 
‘‘ 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. eaed as if on stilts, having gradually 
acquired long, naked legs, which are ‘denuded of 
feathers up to the thighs and often above them 
(Systeme des Animaux sans Vericbres, p. 16). 
“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 
