342 DARWINISM STATED BY DARWIN HIMSELF. 



IIVINO DESCEirDANTS OF FOSSIL SPECIES. 



p It may be asked in ridicule, -whetlier I sup- 



pose that the megatherium and other allied 

 huge monsters, which formerly lived in South America, 

 have left behind them the sloth, armadillo, and ant-eater, 

 as their degenerate descendants. This can not for an 

 instant be admitted. These huge animals have become 

 wholly extinct, and have left no progeny. But in the 

 caves of Brazil there are many extinct species which are 

 closely allied in size and in all other characters to the 

 species still living in South America ; and some of these 

 fossils may have been the actual progenitors of the living 

 species. It must not be forgotten that, on our theory, 

 all the species of the same genus are the descendants of 

 some one species ; so that, if six genera, each having 

 eight species, be found in one geological formation, and 

 in a succeeding formation there be six other allied or 

 representative genera each with the same number of 

 species, then we may conclude that generally only one 

 species of each of the older genera has left modified de- 

 scendants, which constitute the new genera containing 

 the several species ; the other seven species of each old 

 genus having died out and left no progeny. Or, and this 

 will be a far commoner case, two or three species in two 

 or three alone of the six older genera will be the parents 

 of the new genera : the other species and the other whole 

 genera having become utterly extinct. In failing orders, 

 with the genera and species decreasing in numbers as is 

 the case with the Edentata of South America, still fewer 

 genera and species will leave modified blood-descendants. 



