•206 MISCELLANEOUS OBJECTIONS TO THE 



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

 shoveller, 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 tear- 

 ing solid food. The beak of a goose, as I may add, 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. 



Returning to the whales. The Hyperoodon bidens is 

 destitute of true teeth in an efficient condition, but its palate 

 is roughened, according to Lacepede, with small, unequal, 

 hard points of horn. There is, therefore, nothing improb- 

 able in supposing that some early Cetacean form was 

 provided with similar points of horn on the palate, but 

 rather more regularly placed, and which, like the knobs on 

 the beak of the goose, aiding it in seizing or tearing its food. 

 If so, it will hardly be denied that the points might have 

 been converted through variation and natural selection into 

 lamellae as well developed as those of the Egyptian goose, 

 in which case they would have been used both for seizing 

 objects and for sifting the water ; then into lamellae like 

 those of the domestic duck ; and so onward, until they be- 

 came as well constructed as those of the shoveller, in which 

 case they would have served exclusively as a sifting ap- 

 paratus. From this stage, in which the lamellae would be 

 two-thirds of the length of the plates of baleen in the 

 Balaenoptera rostrata, gradations, which may be observed in 

 still-existing Cetaceans, lead us onward to the enormous 

 plates of baleen in the Greenland whale. Nor is there the 

 least reason to doubt that each step in this scale might have 

 been as serviceable to certain ancient Cetaceans, with the 

 functions of the parts slowly changing during the progress 

 of development, as are the gradations in the beaks of the 

 different existing members of the duck-family. We should 

 bear in mind that each species of duck is subjected to a 

 severe struggle for existence, and that the structure of every 

 part of its frame must be well adapted to its conditions of 

 life. 



The Pleuronectidae, or Flat-fish, are remarkable for their 

 asymmetrical bodies. They rest on one side — in the 

 greater number of species on the left, but in some on the 

 right side; and occasionally reversed adult specimens occur. 

 The lower, or resting-surface* resembles at first sight the 



