PHYSICAL CONDITIONS IN GENESIS OF SPECIES. 393 



These premises being admitted — and they are certainly within the 

 bounds of reasonable conception — only the element of time appar- 

 ently is requisite for the . development of an endless varietj^ of un- 

 stable forms, constantly increasing in number and following diver- 

 gent lines of development, and thus capable apparently of giving 

 rise to all the diversity of organisms at present peopling the earth. 



But there are many adverse circvnnstances with which the favored 

 forms have in the outset to contend and to which in the majority of 

 instances they must succumb. These are, first, the minuteness of the 

 first favorable divergence, the isolation of the individuals in which it 

 appears, and consequently the impossibility of such individuals pair- 

 ing with others similarly favored, and the consequent tendency of 

 the offspring to possess the favorable characters in a less rather than 

 in a greater degree than the parent, and to be absorbed into the origi- 

 nal stock. Secondly, in case the incipient advantages are perpetu- 

 al ted, as it is necessary to suppose, the new offshoot must originate 

 from a single point and spread thence gradually to contiguous re- 

 gions as its representatives sloAvly multiph\ 



But it is supposed, again, that new^ forms are not always thus 

 gradually evolved from minute beginnings, but sometimes — perhaps 

 not infrequenth' — arise by a scdtus; that individuals may be born 

 widely different from their parents, differing so widely and persist- 

 ently as not to be so readily absorbed by the parental stock. In proof 

 of this instances are cited of new species apj^arently appearing sud- 

 denly and of varieties thus originating under artificial conditions 

 resulting from domestication. Granting that new forms may thus 

 arise, although as yet few facts have been adduced in its support, 

 they are necessarily at first local and in no way accord w^ith the ob- 

 served geographical differences that characterize particular regions 

 and M-hich affect similarly many species belonging to widely different 

 groups. 



The direct influence of climatic or geographical conditions upon 

 animals is, in the main, ignored by the leading exponents of the doc- 

 trine of natural selection. To quote Mr. Darwin's own words on this 

 point : 



The action of climate seems at first siglit to be quite iudepeudent of tlie strug- 

 gle for existence ; but, in so far as climate chiefly acts in reducing food, it 

 l)rings on the most severe struggle between the individuals, whether of the 

 same or of distinct species, which subsist on the same kind of food. Even when 

 climate — for instance, extreme cold — acts directly, it will be the least vigor- 

 ous, or those which have got the least food through the advancing winter, which 

 will suffer most. When we travel from south to north or from a dani]) region 

 to a dry, we invariably see some species gradually getting rarer aiid rarer and 

 finally disappearing, and the change of climate being consiticuous. we are 

 tempted to attribute the whole effect to its direct action. But this is a false 



SM 1905 29 



