84 THE ZOOLOGIST. 



the dorsal surface of the snout, and on the outer edge of each 

 ramus of the mandible from the tip to near the eye is another 

 row of hairs. Most of the Toothed Whales, such as the Pilot- 

 Whale, White-backed Dolphin, Porpoise, and Common Dolphin,* 

 in their embryonic condition, show similar hairs, but Delphin- 

 aptei'us and Monodon do not. In some again a series of pits 

 (forming a circlet) are also present in the upper jaw, passing 

 through the coloured or pigmented region of the horny layer of 

 the skin, but whether these represent hair-follicles is unknown. 

 The late Sir William Flower, one of the most distinguished 

 authorities on the whales in this country, as well as recent Con- 

 tinental observers, such as Kiikenthal and others, consider that 

 the presence of such hairs indicates that probably the ancestors 

 of the modern whales were much more hirsute. Besides hairs, 

 two species of porpoise, namely, the common form and P. spini- 

 pinnis, from the western shores of South America, present spines 

 on the dorsal fin, the latter on the back as well as on the front 

 of the fin ; whilst Neomeris, a porpoise from the Southern 

 Atlantic, Indian and Pacific Seas, has a series of dermal ossicles 

 in several rows along the dorsum throughout the greater part of 

 its length. So far as observed in young porpoises at St. Andrews, 

 the spines or tubercles are much less developed than in the 

 adult, so that this species does not fall in with the notion of 

 *' inheritance from a more completely armoured ancestor."! The 

 figure of the dorsal fin of the Common Porpoise, as copied from 

 Kiikenthal, differs materially in its posterior outline from any- 

 thing observed in Scotland. 



In regard to the structure of the skin, a well-developed 

 corium (true skin, cutis vera) is absent in most Cetaceans which 

 have a thin horny layer, and the Malpighian layer is much 

 developed and has long papillae. The glands of the skin are 

 generally absent, as are also the muscles, while the cutaneous 

 nerves are sparingly developed. The smoothness of the surface 

 of the whales is probably associated with their surroundings, 

 since a mammal with a smooth skin seems to be better adapted 

 for a purely aquatic life than a hairy one. The further struc- 

 ture of the skin will come under notice when dealing with the 



''•- Prof. D. J. Cunningham. 



f Beddard (after Kiikenthal), vide ' A Book of Whales,' pi. ii. fig. 6. 



