512 POPULAR SCIENCE MONTHLY. 



phosphorescent organs which serve as a lamp to light the pathway of 

 these strange creatures in their strange surroundings. Such adapta- 

 tions can hardly be conceived as possible, save with the very gradual 

 shifting from lighter to darker regions through the lapse of thousands 

 and thousands of years. 



In modern times, since man's domination began, another factor has 

 appeared, and its influence in modifying animal forms and structure 

 has been one of the most potent and striking for such as have fallen 

 within its scope. While man's effort has been largely to exterminate 

 the lower forms of life, especially those inimical to his interest, he has 

 utilized others for his service, and in the process of domestication we 

 may see compressed into brief time such changes as under natural con- 

 ditions would have occupied untold years, if, indeed, they would ever 

 have been possible, since many of these changes unfit the forms for sur- 

 vival under natural conditions. So potent this factor that the immor- 

 tal Darwin used its results as furnishing some of the most conclusive 

 testimony for the theory of natural selection, believing that what could 

 be accomplished in brief time by artificial, or human, selection could 

 be accomplished in greater time by natural selection. 



To see the power of this factor we may compare the various breeds 

 of cattle and refer all to the primitive form from which we have abso- 

 lute historic evidence that they were derived. The breeds of horses are 

 equally striking, as the immense draft horse, the Shetland pony, the 

 thoroughbred racer and the Arabian with hosts of special strains will 

 attest. So, too, with dogs, cats and fowls. The pigeon which fur- 

 nished Darwin with so much evidence since the native rock pigeon, the 

 extreme breeds of fantails, carriers, etc., can be seen side by side and 

 their relationship unquestionably fixed. Now I wish particularly to 

 call attention to the fact that many of these domesticated forms, as a 

 result of their domestication, have been unfitted for life in other 

 spheres, and if dropped from the fostering care of man would almost 

 certainly suffer rapid extermination, those surviving being the ones 

 that had been least affected by the process of domestication. A modern 

 hog would stand a poor show, but the southern razor-back doubtless 

 would survive, for a considerable period at least, without man's assist- 

 ance. Here then is a by-path opened in very recent time and into 

 which certain animals have been driven by man, seldom of their own 

 choice, if ever, the confines of which have profoundly modified many 

 and behind them the gates have been closed never to be opened again. 



Pushing away from the congenial temperatures of equatorial and 

 temperate regions, life ventures into the inhospitable frozen zones of 

 the polar regions, and by adaptation to such clime invades the most 

 forbidding sphere. Earth's 'warm embrace' is here a 'cold reception,' 

 but hosts of birds, mammals, fishes and insects have become established 



