62 ANIMAL LIFE PAST AND PRESENT. 



The second group, containing the Whales, Porpoises, 

 Grampuses, Dolphins, &c., differs so remarkably from 

 all other Mammals that it has been referred to a dis- 

 tinct order the Cetacea. All the members of this 

 group (Fig. 14) have, indeed, assumed such a completely 

 fish-like appearance that it is even now frequently 

 difficult to convince people that they are true Mammals. 

 Their mammalian nature is, however, shown by their 

 warm blood and four-chambered heart, by the circum- 

 stance that they produce their young in a living con- 

 dition and nourish them by milk drawn from the udder 

 of the parent, and also by their respiration being 

 effected by the aid of lungs. The "spouting" of 

 Whales as they come to the surface is, indeed, mainly 

 due to the water of the sea being thrown up as the 

 air from the lungs is forcibly expelled from the 

 nostrils before the animal has quite reached the 

 surface. We may add that the certainty that Whales 

 are true members of the mammalian class is one 

 of the strongest reasons against employing the term 

 " quadrupeds " to denote that division of Vertebrates. 



Although, as aforesaid, the general appearance of a 

 Whale or Porpoise is fish-like, yet a more careful 

 examination shows certain very important points of 

 difference. In the first place, the tail-fin, or " flukes " 

 as it is termed by whalers, is expanded horizontally 

 instead of vertically. The reason for this horizontal 

 expansion appears to be owing to the necessity the 

 Whale is under of coining rapidly to the surface for 

 the purpose of breathing ; the upward and downward 



