14 Geographical Distribution of Animals. 



in a reference to the different animals which man has thus 

 made subservient to his social condition. We shall here 

 allude only to the laws of distribution of wild animals in 

 their natural condition. 



It has already been stated, that the present distribution of 

 animals agrees with the distribution of extinct types belong- 

 ing to earlier geological periods, so that the laws which regu- 

 late the geographical distribution of animals seem to have 

 been the same at all times, though modified in accordance 

 with the successive changes which the animal kingdom has 

 undergone from the earliest period of its creation to the pre- 

 sent day. The universal law is, that all animals are circum- 

 scribed within definite limits. There is not one species which 

 is uniformly spread all over the globe, either among the 

 aquatic races or among the terrestrial ones. Of the special 

 distribution of man, who alone is found everywhere, we shall 

 speak hereafter. The special adaptation of animals to cer- 

 tain districts is not merely limited to the individual species. 

 We observe a similar adaptation among genera, entire fami- 

 lies, and even whole classes. For instance, all Polypi, Me- 

 dusce, and Echinoderms, that is to say all Badiata^ without 

 exception, are aquatic* That large group of animals has not 

 a single terrestrial representative upon any point of the sur- 

 face of the globe ; and during all periods of the history of 

 our earth, we find that they have always been limited to the 

 liquid element. And they are not only aquatic, they are 

 chiefly marine, as but exceedingly few of them are found in 

 fresh waters. Among Mollusca we find almost the same 

 adaptation. Their element also is the sea. The number of 

 fresh-water species is small, compared with that of marine 

 types ; and we find terrestrial species in only one of their 

 classes. In former periods, also, Mollusca were chiefly marine ; 

 fluviatile and terrestrial types occurring only in more recent 

 periods. 



* The following statements have been strictly considered, and are made in 

 reference to a revised classification of the animal kingdom, the details of which 

 must, however, be omitted here, as they would extend this article beyond our 

 allotted bounds. 



