368 Professor Flower [^Jf^s-J 25, 



species of whales, show very marked varieties of progress, from a 

 simple comparatively rudimental and imperfect condition, to what is 

 perhaj)s the most wonderful example of mechanical adaptation to 

 purpose known in any organic structure. These variations are worth 

 dwelling upon for a few minutes, as they illustrate in an excellent 

 manner the gradual modifications that may take place in an organ, 

 evidently in adaj)tation to particular requirements, the causation of 

 which can be perfectly explained upon Darwin's principle of natural 

 selection. 



In the Eorquals or fin- whales (genus Balsenoptera), found in 

 almost all seas, and so well known otf our own coasts, the largest 

 blades in an animal 70 feet long do not exceed 2 feet in length, 

 including their hairy terminations ; they are in most species of a 

 pale horn colour, and their structure is coarse and inelastic, sepa- 

 ratinfT into thick, stiti* fibres, so that they are of no value for the 

 ordinary purposes to which whalebone is applied to the arts. These 

 animals feed on fish of considerable size, from herrings up to cod, 

 and for foraging among shoals of these creatures the construction of 

 their mouth and the structure of their baleen is evidently suflicient. 

 This is the type of the earliest known extinct forms of whales, aud it 

 has continued to exist, with several slight modifications, to this day, 

 because it has fulfilled one purpose in the economy of nature. Other 

 purposes for which it was not sufiicient have been supplied by gradual 

 changes taking place, some of the stages of which are seen in the 

 intermediate conditions still exhibited in the Megaptera, and in the 

 Atlantic and Southern Eight Whales. Before describing the extreme 

 modifications in the direction of complexity, I may mention, to show 

 the range at present presented in the development of baleen, tliat 

 there has lately been discovered in the North Pacific a species called 

 by the whalers the Californian Grey "Whale (^Unchianectes glaucus), 

 which shows the opposite extreme of simplicity. The animal is from 

 30 to 40 feet in length ; the baleen blades are only 182 on each side 

 (according to Scammon) and far apart, very short (the longest being 

 from 14 to 16 inches in length), light brown or nearly white in 

 colour, and still more coarse in grain and inelastic than that of the 

 Eorquals. The food of these whales is not yet known with certainty. 

 They have been seen apparently seeking for it along soft bottoms of 

 the sea, and fuci and mussels have been found in their stomachs. 



In the Greenland Eight Whale of the circumpolar seas, the Bow- 

 head of the American whalers [Balcena mysiicetus), all the peculiarities 

 which distinguish the head and mouth of the whales from other 

 mammals have attained their greatest development. The head is of 

 enormous size, exceeding one-third of the whole length of the creature. 

 The cavity of the mouth is actually larger than that of the body, 

 thorax, and abdomen together. The up2)er jaw is very narrow, but 

 greatly arched from before backwards, to increase the height of the 

 cavity and allow for the great length of the baleen, the enormous 

 rami of the mandibles are widely separated posteriorly, and have a 



