CETACEA. 555 



Order 5. CETACEA.* 



Aquatic, fish-like, naked forms witlioiit hind limbs. The head 

 passes continuously into the body and the nasal apertures are on 

 the top of the head. 



The Cetacea are entirely aquatic animals. Though fish-like 

 in appearance, they are mammalian in structure, but they stand 

 far apart from other mammals, and it is impossible to guess at 

 their origin. Some species attain a colossal size, and are among 

 the largest, if not the largest, of all known animals, whether living 

 or extinct. The cervical region of the vertebral column is 

 extremely short, and there is apparently no neck, the head 

 passing directly into the trunk. There is a horizontally- ex- 

 panded caudal fin (the lateral expansions of which are called 

 flukes), and often a fatty dorsal fin. Hairs are almost entirely 

 absent, being represented only by a few bristles on the upper 

 lip, which are present during the whole of life or only during 

 the foetal period, and are without sebaceous glands. On the 

 other hand there is developed beneath the thick skin in the 

 subdermal cellular tissue a considerable layer of fat (blubber), 

 which to a certain extent takes the place of fur and serves both 

 to prevent the loss of heat and to diminish the specific gravity. 

 It does not, however, necessarily follow that the absence of hair 

 is caused by the presence of blubber, for m the seaLs both hair 

 and blubber are present. The absence of hair is a property 

 of the whale, and cannot be accounted for. The same remark 

 applies to the scanty hairy covering found in some other 

 mammals. The head is large, and the openmg of the 

 external ear is very minute and without a pianna. The eyes are 



* Hunter, Observations on the strtTcture and oeeonomy of whales. 

 Phil. Trans., 1787. F. Cuvier, Histoire naturelle des Cetaces, Paris, 1836. 

 D. F. Eschricht. Unters. uber die nordischen Walthiere, Leipzig, 1849. 

 d". F. Eschricht eg J. Reinhardt, Om Nordhvalen, Copenhagen, 1861. 

 van Beneden and Gei-vais, Osteogrriphie des Cetaces viv. et foss., 1868-1880, 

 1 vol. and atlas 64 plates, van Beneder, Histoire Nat. des Cetaces des 

 mers d' Europe, 1 vol. 8vo, 1889. C. M. Scammon, Marine Animals oj 

 the N.W. coast of N. America, 1874. J. F. Brandt, Unters. lib. die foss- 

 u. subfoss. Cetaeeen Europa's, Mem. Acad. Petersbourg, (7), 20, and 21, 

 1873-4 W H Flower, On the characters and divisions of the famihes 

 of the Delphinidae. Proc. Zool. Soc, 1883, p. 466. jF. W. True, Re%dew 

 of the Family Delphinidae, Bull. U. S. Nat. Mus., 1889. R. Lydekker, 

 Cetacea of the Suffolk Crag, Quart. Journ. Geol. Sac, 42, 1887, p. 7, and 

 Catalogue of the fossil mammalia in the British Museum, 1887. F. E. 

 Beddard, A Book of Whaler, London, 1900. 



