FUNDAMENTAL RELATIONS OF ANIMALS 21 



the reach of the mental powers of man, and if man himself is part 

 and parcel of the whole system, how could this system have been 

 called into existence if there does not exist One Supreme Intelligence 

 as the Author of all things? 



SECTION V 



CORRESPONDENCE IN THE DETAILS OF STRUCTURE IN ANIMALS 

 OTHERWISE ENTIRELY DISCONNECTED 



During the first decade of this century naturalists began to study 

 relations among animals which had escaped almost entirely the at- 

 tention of earlier observers. Though Aristotle knew already that the 

 scales of fishes correspond to the feathers of birds,^*^ it is but recently 

 that anatomists have discovered the close correspondence which exists 

 between all the parts of all animals belonging to the same type, how- 

 ever different they may appear at first sight. Not only is the wing of 

 the bird identical in its structure with the arm of man or the fore 

 leg of a quadruped, it agrees quite as closely with the fin of the whale 

 or the pectoral fin of the fish, and all these together correspond in 

 the same manner with their hind extremities. Quite as striking a 

 coincidence is observed between the solid skull-box, the immovable 

 bones of the face and the lower jaw of man and the other mammalia, 

 and the structure of the bony frame of the head of birds, turtles, liz- 

 ards, snakes, frogs, and fishes. But this correspondence is not limited 

 to the skeleton; every other system of organs exhibits in these animals 

 the same relations, the same identity in plan and structure, whatever 

 be the differences in the form of the parts, in their number, and even 

 in their functions. Such an agreement in the structure of animals is 

 called their homology and is more or less close in proportion as the 

 animals in which it is traced are more or less nearly related. 



The same agreement exists between the different systems and their 

 parts in Articulata, in Mollusks, and in Radiata, only that their struc- 

 ture is built up upon respectively different plans, though in these 

 three types the homologies have not yet been traced to the same 



^'' Aristoteles, Historia Animalium, Lib. I., Chap. 1, Sect. 4 [486'': ". . . for what the 

 feather is in a bird, the scale is in a fish."] 



