Species of the Secondary and Tertiary Formations ? 257 



like manner, evading the attacks which were made upon it. 

 The establishment of Europeans in the island of Mauritius, 

 has thus been the principal cause of the disappearance of 

 the Dodo, just as the clearing away of the forests which 

 covered the surface of ancient Germany has occasioned the 

 loss of one of the most remarkable animals of our world. 



Many of the animals figured or sculptured on the monu- 

 ments of antiquity, and uniting conditions which render their 

 existence possible, have no longer representatives, as is also 

 the case with certain species buried in the ancient catacombs 

 of Egypt. GeofFroy Saint Hilaire has sought in vain in that 

 country for traces of the two crocodiles which he found em- 

 balmed in the Egyptian tombs. These two races, named by 

 him Crocodilus lacunosus and Crocodilus complanatus, are still 

 to be sought for among the living races. 



There is no need, therefore, of extraordinary causes in or- 

 der to destroy certain species ; it is sufficient to bring about 

 this result, that the species cannot escape our pursuits, nor 

 defend themselves against our attacks. It is obvious that 

 they become extinct, so much the more speedily if their fe- 

 cundity be inconsiderable, and the number of deaths exceeds 

 that of births. The loss of a species may, therefore, depend 

 on the simplest circumstances, and be the effect of causes by 

 no means beyond the ordinary course of things. 



When we study, as a whole, the organized beings which 

 in their turn have animated the world, which, from the sub- 

 ject of our investigations, we are struck with the permanency 

 of the generic types. A pretty considerable number of these 

 types, often very natural, have run through all the ages with 

 the same characters, and have undergone alterations only in 

 their specific distinctions. The species of these persistent 

 genera have only differed from one epoch to another, and 

 most of all from the ancient creations to the present ones. 

 There are, however, many races of our own times which have 

 preserved the same characters which distinguish those of the 

 first ages. 



The greatest variations, then, have taken place, not in the 

 generic type, but in the specific type which characterizes, and 

 forms the difference between organized beings, all the indi- 



