SWIMMING ANIMALS. 57 



the maximum power in propelling the animal through 

 the water. 



There are six chief groups of swimming birds, 

 namely, the Ducks, Geese, and Swans (Anseres) ; the 

 Pelicans, Cormorants, and Darters (Steganopodes) ; the 

 Gulls (Gaviae) ; Petrels (Tubinares) ; the Divers, Auks, 

 and Grebes (Pygopodes) ; and the Penguins (Impennes). 

 There are, however, a few members of other groups, 

 such as the Dipper among the Passerines, and the Coot 

 among the Eails, which are also expert divers and 

 swimmers. The circumstance, however, that in neither 

 of these instances is the foot fully webbed that of 

 the Dipper being like the foot of a Thrush, and that 

 of a Coot only having web-like expansions on the sides 

 of the toes indicates that the aquatic habits of these 

 birds are of comparatively recent acquisition, and 

 have not induced any strongly marked structural pecu- 

 liarities. 



The Anseres include by far the greater number of 

 swimming birds, and the admirable adaptation of their 

 form and structure to their mode of life is so well 

 known as to require no further mention. The Pelicans 

 and their allies differ from that group in that the web 

 includes all the four toes of the foot (Fig. 18), instead 

 of only the three front ones. In this group the 

 Frigate Bird has a shorter leg than any bird of equal 

 size. The Darters, or Snake-Birds, of which there are 

 four species found in the warmer regions of the globe, 

 and of which examples are generally to be seen in 

 the Zoological Society's Gardens, are, however, those 



