210 WHALES, PAST AND PRESENT xv 



or vestiges of a past condition, become useless owing to change 

 of circumstances and environment, and undergoing the process 

 of gradual degeneration, preparatory to their final removal 

 from an organism to which they are only, in however small a 

 degree, an incumbrance, or are they incipient structures, 

 beginnings of what may in future become functional and 

 important parts of the economy ? These questions will call 

 for an attempt at least at solution in each case as we proceed. 



Before entering upon details, it will be necessary to give 

 some general idea of the position, limits, and principal 

 modifications of the group of animals from which the special 

 illustrations will be drawn. The term " whale " is commonly 

 but vaguely applied to all the larger and middle-sized Cetacea, 

 and though such smaller species as the dolphins and porpoises 

 are not usually spoken of as whales, they may for all intents 

 and purposes of zoological science be included in the term, 

 and will come within the range of the present subject. Taken 

 altogether the Cetacea constitute a perfectly distinct and 

 natural order of mammals, characterised by their purely 

 aquatic mode of life and external fishlike form. The body is 

 fusiform, passing anteriorly into the head without any distinct 

 constriction or neck, and posteriorly tapering off gradually 

 towards the extremity of the tail, which is provided with a 

 pair of lateral pointed expansions of skin supported by dense 

 fibrous tissue, called " flukes," forming together a horizontally- 

 placed, triangular propelling organ. The fore -limbs are 

 reduced to the condition of flattened ovoid paddles, incased 

 in a continuous integument, showing no external sign of 

 division into arm, forearm, and hand, or of separate digits, 

 and without any trace of nails. There are no vestiges of 

 hind -limbs visible externally. The general surface of the 

 body is smooth and glistening, and devoid of hair. In nearly 

 all species a compressed median dorsal fin is present. The 

 nostrils open separately or by a single crescentic valvular 

 aperture, not at the extremity of the snout, but near the vertex. 



Animals of the order Cetacea abound in all known seas, 

 and some species are inhabitants of the larger rivers of South 

 America and Asia. Their organisation necessitates their life 

 being passed entirely in the water, as on the land they are 



