14 SArri;i)AY i.ecturk«. 



sented in the fish, the digits being i)r(jbably, but only very 

 distantly, repeated in the salmon by the rays, and the meta- 

 carpals by the bones at the base thereof; the bones of the 

 arm — the radius and ulna as well as liumorus — are entirely 

 wanting. The single scapular or blade bone of the whale, 

 on the other hand, is represented by at least four pieces, and 

 connected ^yith the arch of the fish are several other and 

 accessory pieces. 



I have thus dwelt upon the fins because if any part in 

 the whale would show fish-like modifications, these parts 

 would, from their relations to the surrounding medium, be 

 naturally most liable to exhibit such adaptation. Upon the 

 other points in the structure of the two types we cannot delay 

 so long. 



The shoulder girdle, as we have seen, is connected with 

 the skull in the fishes, and let us take up the consideration 

 of that next. 



Look first at the whale's skeleton ; note that the skull, as 

 in man's, is one compact mass, composed of many bones^ 

 but all closely connected with their neighbors save the 

 lower jaw. The lower jaw is directly articulated with the 

 skull, and it is also especially to be noticed that its branches 

 are undivided or single bones. Let me add as an item of 

 information which I must ask you to take on trust that 

 there are ear bones which, though much modified, agree 

 essentially with those of quadrupeds. 



Turn now to the fish's skull ; you will at once perceive that 

 the skull, contrasted with the mammal's, is much broken 

 up. It has a brain box, but that does not at all represent 

 the entire skull of the mammals. The upper jaw bones, the 

 palate bones, and others, are separate. The lower jaw has 

 each of its branches composed of four separable elements, 

 and those branches, you will see, have no direct connection 

 with the brain-box, but are separated by the intervention of 

 a chain of large bones which are not to be seen at all in the 

 whale's skull. But, nevertheless, those bones are repre- 

 sented in the whale's head, and the bones forming the sus- 

 ponsorium, as it is called, of the lower jaw have their repre- 



