11 



If not to a conception of grand, orderly evolution, to 

 ■what do facts such as these tend ? If from all our premises 

 we accept not this conclusion, then by all logic are we 

 bound to regard the universe as a kind of whimsical sorcery, 

 a sad and pointless joke. 



For my third series of evidences I will select the argument 

 based on Structure. Among those creatures which are known 

 as fishes to the popular mind, whales, porpoises, seals, sea- 

 lions, and some others, are structurally as diflFerent from the 

 ordinary population of the deep as dogs and cats are from 

 pike and roach. 



The gradual change of life from terrestrial to aquatic 

 habits necessitated, it is true, correspondingly great changes 

 of structure in these creatures. The bones became altered 

 in shape, the more modifiable organs — the skin, the hair, 

 the teeth — underwent great changes. The limbs became 

 shortened or disappeared. The most useful form, the fish 

 form, allowing swift progress through the water, was, by 

 the process of natural selection, assumed. But these animals 

 still breathe air and suckle their young ; and no natui'ahst 

 now classifies the cetacea and sirenia with fishes. On the 

 evidence of structure alone, they are mammalia. No 

 naturalist can admit a shadow of doubt on the point, any 

 more than he would dream of associating bats with birds 

 because they both fly, or crocodiles and rhinoceroses together, 

 and these with beetles, because they are all protected by a 

 horny case. 



Take, again, the fore-limb of vertebrata. It consists of 

 a single arm-bone', the humerus ; two fore-arm bones, the 

 radius and ulna ; several wrist-bones f oi-ming a carpus, and 

 a variable number of digits, usually five in the higher series. 

 Yet this appendage, while retaining this essential structiire, 

 is so modified as to subserve me in writing this address, the 

 monkey in cUmbing trees, quadrupeds in locomotion ; it 

 supports the wing of the bat, and enables it to fly ; the fin 

 of the porpoise, and enables it to swim. The human arm 

 and leg, again, which are differentiated to fulfil such diflferent 

 purposes, are nevertheless homologues in structure and 

 correspond to one another, bone to bone. In the words 

 of Huxley, " Large groups of species of widely different 

 habits present the same fundamental plan of structure ; 

 and parts of the same animal or plant, the functions of 

 which are very diif erent, likewise exhibit modifications of a 

 common plan." 



