330 



VEUTEBUATE ANIMALS. 



uiiilev tlie skin, and serves to protect tlie body from cold. Though 

 ail inhabitant of the sea, the Whale i-i obliged to come to the surface 

 to breathe, and in so d(.iiiig it ejects from the blow-hole what looks 

 like a column of water, the whole operation being known to the 

 whalers as " blowing." The true nature of this act is now hardly 

 questionable, and it appears certain that the a]jparent jet of water 

 is ill reality, mainly if ncjt entirely, due to the condensation of the 

 moisture which is contained in the air expelled from tlie lungs. 

 The old view was that "blowing" consisted in the Whale ejecting 

 through the nose the water which had previously been filtered 

 through the baleen-])lates of the mouth ; but it appears to be quite 

 certain that this view, at any rate, is not the correct one. The 

 Eorcpials or Finner Whales resemble the Greenland Whale in most 

 respects, but the skin is furrowed with deep plaits or folds, and there 

 is a dorsal tin, placed on the back. 



Fig. L*;5l5. — Cctacea. The common Dolijliiii (Delpliinus delphu). 



size (eighty feet or more), but they are seldom captured, as their 

 commercial value is small. 



The Toothed Whales (Odontoceli) are best known liy the Sperm 

 Whale (tig. 235), an animal as large oi' larger than the Greenland 

 Whale, but distinguished by having numerous ccmical teeth, a single 

 blow-hole, and a curiously truncated head. Sperm Whales yield 

 an excellent oil, and the singular fatty sub.stance which is known as 

 "sperm;i,ceti," They also yield the substance called "ambergris," 

 which is used as a ])erfiiii]C ; but this is |ivi)liably a product of di.sease. 



Tlie last family of the Ceturi'a needing mention is that of the 

 DdpJtiiiiihif, cnmprisiiig tlie Doljihins (tig. 236) and Porpoises. They 

 have numerous coiiic:al teeth in V>oth jaws, and the nostrils open by 

 a single aperture on the to]i of the head. The Dolphins are mostly 

 inhabitants of the sea, but there are fresh-water forms which inliabit 

 the rivers of South America and Sontliern Asia. The Porpoises are 

 exclusively marine, and occur in all seas. The most remarkable of 

 the DdfiliiiililiK is the Narwhal or Sea-unicorn, which is found in 



