244 THE POPULAR SCIENCE MONTHLY. 



of the length of the head of such a whale, so that the difference in size 

 between the duck's lamellae and the imperfect baleen-plates of this 

 whale is not markedly disproportionate, after all. After the examina- 

 tion of the beaks of various species of swimming-birds, Mr. Darwin 

 arrives at the conclusion that " a member of the duck family with a 

 beak constructed like that of the common goose, and adapted solely 

 for grazing, or even a member with a beak having less well-developed 

 lamellae, might be converted by small changes into a species like the 

 Egyptian goose (which partly grazes and partly sifts mud) this into 

 one like the common duck and, lastly, into one like the shoveler, 

 provided with a beak almost exclusively adapted for sifting the water ; 

 for this bird could hardly use any part of its beak, except the hooked 

 tip for seizing or tearing solid food. The beak of a goose, as I may 

 add," says Mr. Darwin, " might also be converted by small changes 

 into one provided with prominent recurved teeth, like those of the 

 Merganser (a member of the same family), serving for the widely 

 different purpose of securing live fish." 



Mr. Darwin next endeavors to apply the moral of this interesting- 

 sketch of probable modification of the bills of ducks to the case of the 

 whales. If the stages of modification in these animals are hypotheti- 

 cally so clear, may not the case of the whalebone-bearing whales be 

 susceptible of like explanation ? A certain whale (JETyperoddon) be- 

 longing to a small group known popularly as the "beaked whales," 

 from the possession of a prominent beak or snout, has no true teeth, 

 but bears rough, unequal knobs of horny nature in its palate. Here, 

 therefore, is a beginning for the work of selection and development. 

 Granted that these horny processes were useful to the animal in the 

 prehension and tearing of food, then their subsequent development 

 into more efficient organs is a warrantable inference if the order of 

 living nature teaches us aright. From rudimentary knobs, a further 

 stage of development would lead to an increase in which they may 

 have attained the size of the lamellae of an Egyptian goose, which, as 

 already remarked, are adapted both for sifting mud and for seizing 

 food. A stage beyond, and we reach the shoveler's condition, "in 

 which the lamellae would be two thirds of the length of the plates of 

 baleen," in a species of whalebone whale {Balamojjtera) possessing a 

 slight development of these organs. And from this point, the further 

 gradations leading onward to the enormous developments seen in the 

 Greenland whale itself, are easily enough traced. Hypothetically, 

 therefore, the path of development is clear enough. Even if it be re- 

 marked that the matter is entirely one of theory, not likely to be ever 

 partly verified, far less proved at all, we may retort that any other ex- 

 planation of the development of the organs of living beings, and of 

 living beings themselves, must also be theoretical in its nature and 

 as insusceptible of direct proof as are Mr. Darwin's ideas. But the 

 thoughtful mind must select a side, and choose between probabilities ; 



