io THE POPULAR SCIENCE MONTHLY. 



Should it be urged that the present tendency toward reducing 

 species be taken as an evidence that species had not before been 

 properly defined, then it offers a stronger argument still in favor of 

 the fact that species are even more variable than had before been 

 supposed, leaving the greater possibility of larger numbers of these 

 ultimately surviving. Again, the assumption that the limitation of 

 specific variation had not been properly indicated, shows how repre- 

 hensible has been the work of some of those who have burdened our 

 literature with their bad species. 



The fact is, the work has in a measure been justifiable, and is 

 not' to be wholly condemned. The workers in this line have followed 

 the teachings of their masters. A group of individuals removed 

 from an allied group of individuals by an extra dot or darker shade, 

 perpetuating their kind from generation to generation, marked with 

 persistent characters, and in every way coming up to the standard 

 recognized as specific, had the right to be judged as such. It is only 

 when a whole series of forms are collected, and climatic influences 

 are seen to affect these in the same way that they affect other groups 

 of species even in different classes, that the mere influence of 

 moisture and temperature is shown to be the sole cause of many of 

 these supposed specific characters. 



Dr. A. S. Packard, in his remarkable monograph of a group of 

 moths, the Phalcenidce, published under the auspices of the Hayden 

 Survey, finds that with some species there are changes analogous to 

 those pointed out by Baird and Allen ; and while he does not find 

 enough to establish a law, yet to his mind enough is seen " to illus- 

 trate how far climatic variation goes as a factor in producing primary 

 differences in fauna? within the same zones of temperature," and he 

 admits that varietal and even specific differences may arise from these 

 climatic causes alone. Dr. Packard, in the same work, under the 

 head of " Origin of Genera and Species," says, " The number of so- 

 called species tends to be reduced as our specimens and information 

 increase." The genera also " are as artificial creations as species and 

 varieties. The work of the systematic biologist often amounts to but 

 little more than putting Nature in a strait-jacket." 



An application of the influence of temperature is here proper, as 

 explaining, on a rational ground, the persistence of peculiar arctic 

 forms of animals and plants on the summits of Mount Washington 

 and other high peaks. With a knowledge of glacial phenomena, we 

 are capable of judging the condition of things which must, of neces- 

 sity, have existed directly after the recedence of the great ice-sheet : 

 its southern border slowly retreating, and, with the encroachment of 

 the warmer zone, the arctic forms dying out, or surviving under 

 changed conditions ; but, in high plateaus and mountains, local 

 glaciers flourished for a while, and at their bases arctic forms flour- 

 ished, and, lingering too long, were ultimately cut off by the retreat 



