46 THE INFANCY OF ANIMALS 



especially attract attention are the records of what are 

 known as vestigial structures, the apparently useless 

 remnants of once functional and well-grown organs. 



Time was when these structures seemed to defy inter- 

 pretation : they were the untranslatable hieroglyphics of 

 pre-Darwinian days. But if we read them, as the master 

 taught us, in conjunction with the records of the rocks, 

 we are able to make of these fragments an intelligible, 

 if imperfect, story of evolution. Illustrations of this fact 

 have already been given in the case of the bony nodules 

 in the skin of the porpoise, for example ; but still more 

 striking are the facts furnished by a study of horns and 

 antlers. 



Horns of ruminants, it must be remembered, first ap- 

 peared as bony " bosses " on the forehead, and gradually 

 assumed a spike-shaped form. Later the peculiar spiral 

 twists and graceful curves, characteristic of the different 

 types displayed by oxen, antelopes, sheep and goats, 

 were evolved. 



To-day, in the individual life of each species, we can 

 actually watch these changes of form from the original 

 pair of spikes — changes which represent the gradual 

 acquirements during enormous periods of time. The 

 nature of such transformations is well displayed in the 

 case of the horns of the gnu, shown in the accompanying 

 photograph. In the calf, it will be noticed, the horns 

 are of the ancestral, upright, or columnar form : in the 

 adult, it will be seen, the bases are enormously thickened, 

 while the horn curves abruptly downwards and then as 

 abruptly upwards. 



Unhappily the white-tailed gnu is almost or quite 

 extinct as a wild animal, so that we can now hardly hope 

 to obtain the whole series of gradations in development 



