242 THE POPULAR SCIENCE MONTHLY. 



and scales of these animals. To what conclusion, then, does this same 

 principle lead us respecting the nature of the baleen-plates in the mouth 

 of the Greenland whale and its allies ? To a sufficiently certain, but 

 at the same time startling thought, is the reply of the comparative 

 anatomist. 



If we examine the structure of the human mouth, or that of animals 

 allied to man, we find that cavity to be lined by a delicate layer named 

 epithelium. This epithelium consists really of a modification of the 

 upper layer of the skin, and we see this modification familiarly in the 

 difference between the skin of the face and the layer which is infolded 

 to form the covering of the lips and the lining membrane of the mouth. 

 No tissue is more familiar to the student of physiology than epithe- 

 lium, composed as it is of epithelial cells or microscopic elements, which 

 in one form or another are found in almost every important tissue of 

 the body. The epithelium is a delicate tissue, as usually seen in man 

 and vertebrate animals ; but in some instances it becomes hardened by 

 the development of horny matter, and may then appear as a tissue of 

 tolerably solid consistence. In the mouth of a cow or sheep, the epi- 

 thelium of part of the upper jaw is found hardened and callous, and 

 there forms a horny pad against which the front teeth of the lower jaw 

 may bite in the act of mastication. It is exactly this epithelial layer, 

 then, which becomes enormously developed in the whalebone whales 

 to form the baleen-plates just described. That this is actually the case 

 is ascertained by the development of the baleen-plates, as well as by 

 their situation and relations to the gum and palate. And the recital 

 becomes the more astonishing- when we consider that, from cells of 

 microscopic size in other animals, structures of enormous extent may 

 be developed in the whales. The baleen-plates possess a highly impor- 

 tant office. They constitute a kind of huge strainer or sieve, the pos- 

 session of which enables the whale to obtain its food in a convenient 

 fashion. Whether or not Biblical scholars and commentators agree in 

 regarding the " great fish " which wrought' calamity to the prophet 

 Jonah as a special creation, and as an entirely different animal from 

 the whale of to-day, the plain fact remains that a whale has a gullet 

 of relatively small size when compared with the bulk of the animal. 

 Fortunately, however, the faith of rational mankind is not pinned to 

 literal interpretation of the untoward incident chronicled in Jonah, 

 and, whale or no whale, it is curious to learn that the largest of ani- 

 mals may in a manner be said to feed on some of the most diminutive 

 of its fellows. In the far north, and in the surface-waters of the Arctic 

 seas, myriads of minute organisms, closely allied to our whelks, and 

 like mollusks, are found. Such are the " Sea-butterflies," or Pteropoda 

 of the naturalist : little delicate creatures which paddle their way 

 through the yielding waters by aid of the wing-like appendages spring- 

 ing from the sides of the head and neck. These organisms are drawn 

 into the mouth of the Greenland whale in veritable shoals, and as the 



