314 TYPES OF ANIMAL LIFE 



thigh bones, though there could have been no external 

 appearance of hind-limbs any more than in the three 

 previously described mermaids. The naturalist Illiger, 

 who gave the rhytina its name, called the small group T 

 have spoken of as mermaids, by the name of Sirens, and 

 the group (order) is now known by naturalists by the 

 term /^irenia. The mode and source of then* evolution 

 are still quite unsolved problems, but there are not 

 wanting indications that they may be collateral descend- 

 ants of elephants and Dhiotheria. If so, they can put 

 in some claim to rank as odd-toed ungulates, absurd and 

 paradoxical as it may seem to reckon among odd-toed 

 hoofed beasts, creatures which have not only no " hoofs/' 

 but no " toes " either ! 



But if we cannot positively say what are the nearest 

 relatives of the mermaids, our predecessors reckoned 

 them as belonging to the group of whales and por- 

 poises — an order termed by naturalists Cetacea. Our 

 " mermaids " were formerly spoken of as the ^' Herbi- 

 vorous Cetacea," to distinguish them from the creatures 

 belonging to the other group of creatures (the whales 

 and porpoises), all of which live on animal food. 



To the consideration of these latter, which are the 

 only true Cetacea, we will now turn. 



They ofler a most wonderful example of the puzzling 

 and often misleading effects which external conditions 

 can sometimes bring about, and are a notable warning 

 how necessary it is when we seek to find out the affinities 

 of the different animals not to rely much upon external 

 characters when these are closely related to their mode 

 of life. AVhales and porpoises were long considered, very 

 naturally, to be '' fishes," and were classed among them 

 even by the great naturalist, Ray. Their general form 

 of body — which is spindle-shaped, with no sign of a neck 



