^^"^ THE NEW EVOLUTION '^^^^ 



which are found in the Oligocene are less widely dif- 

 ferent from each other than are the cats and dogs of 

 the present day. Professor Matthew says that "there 

 is no serious gap in the line through which the dogs 

 are traced back to the Lower Eocene Mmcis, but the 

 Lower Eocene ancestors of the Felidas [cats] are repre- 

 sented only by a number of European genera imper- 

 fectly known and apparently not very close to the 

 direct line of descent." Palaeontologists, however, 

 admit the distinctness of these three groups by placing 

 the cats in one family (Felidas), the dogs in another 

 (Canidae), and the Lower Eocene Carnivora to which 

 they are most closely related in still a third (Miacidas). 



Among the other backboned animals or vertebrates 

 there are no intermediates between turtles and snakes, 

 or turtles and lizards, or snakes and lizards, all of 

 which are reptiles, and in the fishes there are no inter- 

 mediates between the cyclostomes (lampreys and 

 hagfishes), or the teleosts or bony fishes, and any 

 other types. 



It should perhaps be emphasized that discontinui- 

 ties in descent and in relationship are much less con- 

 spicuous and marked among the backboned animals 

 or vertebrates than they are in the large invertebrate 

 groups. In the vertebrates there are no such enor- 

 mous gaps as those between the squid, octopus and 

 nautilus, and the snail or oyster, all of which are 

 mollusks, or between the starfishes, sea-urchins, sea- 

 lilies and sea-cucumbers, all of which are echinoderms. 



All the backboned animals taken together form a 

 very homogeneous group in which the entire struc- 



