DISTRIBUTION OF ORGANISMS. 179 



tatores of Cuvier), where the organization is admittedly the 

 humblest, and to which an approximation from the Turtles 

 has long been acknowledged. In this order, as it is called by 

 Cuvier, there are some genera which present the typical bird 

 form in a strikingly imperfect manner, the feet being placed 

 so far behind the centre of gravity that the animal walks no 

 better than a seal, while the anterior extremities short, and, 

 in some instances, scaled, rather than feathered do not serve 

 for flight, but are used exactly like the paddles of the marine 

 turtles in propelling the body through the water ; often for 

 several hundred yards under it. It unexpectedly appears 

 probable that the Birds are derived solely from this order of 

 the Reptiles, and that this is the cause of their more concen- 

 trated unity of structure. The affinity to that inferior class 

 is certainly less clearly shown than are the affinities which 

 pervade the class itself; but can we be sure that the transition 

 from class to class was always to give intermediate forms, or 

 that these, if given, were necessarily to be preserved, either as 

 living species or as fossils ? The Chelonia present a sufficient 

 variety of characters to have been the sole parentage of the 

 Bird class ; many being fierce and carnivorous, while others 

 are vegetable feeders and of gentle character. They are now 

 chiefly tropical, while the swimming birds are hyperboreal ; 

 but the secondary and tertiary formations show that the che- 

 lonia were once much more widely distributed than they now 

 are. 



The First of the great stirpes is that which gives us the 

 birds most important of all to us the domestic poultry. Its 

 root is in certain of the natatorial families, the Divers (Colym- 

 lidce}, Grebes, &c. These are Swimmers native to the 

 Arctic Ocean, though accustomed to migrate southward in 

 winter. They are immediately followed by the Mergansers, 

 Ducks, Geese, Swans, (AnatidceJ and the Phalleropes (Phal- 

 leropida,} Gallinules, and Coots (Lobipedida), which still 

 preserve the aquatic habits, and the webbed or lobated feet 

 necessary for progression in the water, but tend more to resi- 

 dence in rivers and other inland waters. In these, however, 

 we see a clear separation into three subdivisions, one com- 

 H 2 



