ADDITIONS 175 



skin, starting from those animals which can simply make very long 

 jumps and leading up to those which fly perfectly ; so that ultimately 

 they possess the same faculty of flight as birds, though without having 

 any affinities with them in their organisation. 



Flying squirrels {Sciurus volans, aerobates, petaurista, sagitta, volu- 

 cella) have more recently acquired this habit of extending their wings 

 when leaping, so as to convert their body into a kind of parachute ; they 

 can do no more than make a very long jump by throwing themselves 

 to the bottom of a tree, or leaping from one tree on to another at a 

 moderate distance. Now by frequent repetition of such leaps in the 

 individuals of these races, the skin of their flanks is dilated on each 

 side into a loose membrane, which unites the hind-legs to the fore- 

 legs and embraces a large volume of air ; thus saving them from a 

 sudden fall. These animals still have no membranes between the 

 digits. 



The galeopithecus {Lemur volans) doubtless acquired this habit 

 earher than the flying squirrels {Pteromis, Geoffr.) ; the skin of their 

 flanks is still larger and more developed ; it unites not only the hind- 

 legs with the fore-legs but also the tail with the hind-legs and the 

 digits with each other. Now these creatures make longer leaps than 

 the preceding, and even perform a sort of flight. 



Lastly, the various bats are mammals which probably acquired 

 still earher than the galeopithecus the habit of extending their Umbs 

 and even their digits to embrace a great volume of air, and sustain 

 themselves when they launch forth into the atmosphere. 



From these habits, so long acquired and preserved, bats have derived 

 not only lateral membranes but also an extraordinary lengthening of 

 the digits of their four legs (except the thumb) which are united by 

 very large membranes ; so that these membranes of the hands, being 

 continuous with those of the flanks and those which unite the tail to 

 the two hind-legs, constitute in these animals great membranous wings 

 with which they fly perfectly as we all know. 



Such then is the power of habit : it has a remarkable influence on 

 the shape of the parts and endows animals, which have long contracted 

 certain habits, with faculties not possessed by those which have 

 adopted different habits. 



With regard to the amphibians, of which I spoke above, I should 

 like here to communicate to my readers the following reflections that 

 have been raised in me and ever more strongly confirmed by all the 

 subjects I have dealt with in my studies. 



I do not doubt that mammals originally came from the water, nor 

 that water is the true cradle of the entire animal kingdom. 



We still see, in fact, that the least perfect animals, and they are the 



