WHALES AND THEIR NEIGHBORS. 241 



The furnishings of the mouth of the whales include sundry remark- 

 able structures peculiar to a certain family circle of these animals. 

 Such are the " whalebone "-plates, furnishing a substance familiarly 

 spoken of by everybody, but exemplifying at the same time a kind of 

 material regarding the origin of which a tacit ignorance, sanctioned 

 by the stolid indifference of many years' standing, commonly prevails. 

 Whalebone, or " baleen," is a commodity occurring in one group of 

 these animals only, this group being that of the whalebone whales 

 (Balmnidoe), of which the Greenland or Right whale (Balcena mysti- 

 cetus) is the most noteworthy example. From this whale the whale- 

 bone of commerce is derived ; other and nearly related species such 

 as the Rorquals and Furrowed whales possessing the whalebone- 

 plates in a comparatively rudimentary state. The baleen occurs in 

 the mouth of these whales, and is disposed in a curious fashion. It 

 exists in the form of flat plates of triangular shape, each plate being 

 fixed by its base in the palate. The inner side, or that next the center 

 of the mouth, is strongly fringed by frayed-out whalebone fibers, the 

 outer edge of each plate being straight. A double row of these tri- 

 angular plates of baleen depends in the form of two great fringes from 

 the palate of the whale ; and it would appear that each baleen-plate 

 is in reality a compound structure, being composed of several smaller 

 plates closely united. The largest plates lie to the outer side of the 

 series, and in a full-grown whale may measure from eight to fourteen 

 feet in length, and as many as 250 or 300 plates may exist on each 

 side of the palate. 



The nature of these curious organs forms an appropriate subject of 

 inquiry. It is exceedingly rare in nature to find an animal provided 

 with organs or structures which have no affinity with organs in other 

 and related animals. On the contrary, the. principle of likeness or 

 " homology " teaches us that the most unwonted and curious structures 

 in animal existence are for the most part modifications of common or- 

 gans, or at any rate of parts which are represented under varying forms 

 and guises in other animals. By aid of such a principle we discover 

 that the fore-limb of a horse, the wing of a bird, and the paddle of a 

 whale are essentially similar in fundamental structure, and in turn agree 

 in all necessary details with the arm of man. Through the deductions 

 of this science of tracing likenesses and correspondences between the 

 organs of different animals, the zoologist has been taught that the " air- 

 bladder" or " sound" of the fish is the forerunner of the lung of higher 

 animals an inference proved by the fact that in some fishes, such as 

 the curious Lepidosirens or "mud-fishes" of Africa and South Amer- 

 ica, the air-bladder actually becomes lung-like, not merely in form but 

 in function also. By means of this useful guide to the mysteries of 

 animal structure, we note that the bony box in which the body of the 

 tortoise or turtle is contained is formed by no new elements or parts, 

 but consists chiefly of the greatly modified backbone and of the ribs 



VOL. XV. 16 



