THE PLAYFUL HUMPBACK 



The animals of which I have thus far been writing 

 are classified in the suborder Mystacoceti, or whale- 

 bone whales, and are distinguished from the suborder 

 Odontoceti, or toothed whales, by the possession of 

 two parallel rows of thin, horny plates which hang 

 from the roof of the mouth. These plates, com- 

 mercially called whalebone but properly known as 

 baleen, are growths from the skin much like the claws, 

 finger or toenails of land mammals and are not com- 

 posed of bone but of a substance called "keratin." 

 Each plate is roughly triangular, being wide at the 

 base and narrow at the tip, and has the inner edges 

 frayed out into long fibers; these hair-like bristles 

 form a thick mat inside the mouth and thus the 

 small shrimps and other minute food upon which 

 the baleen whales feed are strained out and eaten. 

 The development of whalebone is one of the most 

 remarkable specializations shown by any living 

 mammal The baleen is, in reality, merely an 

 exaggeration of the cross ridges found in the 

 roof of the mouth of a land mammal and a some- 

 what similar straining apparatus is present in a 

 duck's bill. 



The great majority of people believe that all large 

 whales eat fish whereas none, except the sperm whale, 

 does so when other food is to be obtained. All the 

 baleen whales eat small crustaceans and especially the 

 little red shrimp (Euphausia inermis), which is about 

 three-quarters of an inch long. These minute ani- 

 mals float in great masses, sometimes near the sur- 

 face but often several fathoms below it, and the move- 



