674 ZOOLOGY. 



exposed to human interference may vary when subjected to 

 changes in their environment. Also the fact that man can, by 

 careful selection, breed races of horses adapted for draught, 

 speed, or the road ; races of cows for different qualities of 

 milk ; beeves for meat ; races of sheep for pre-eminence in 

 the quality of their wool or mutton, or races of doves or 

 poultry for beauty, usefulness, or other qualities ; the fact 

 that gentleness, and generally good mental qualities, can be 

 made to replace viciousness in horses, cattle, dogs all these 

 and many other facts, in the art of breeding animals knoAvn 

 to fanciers, indicate that nature has, through the past ages, 

 by the operation of natural laws, evolved races and species 

 of animals which have followed constantly improving lines 

 of development, the outcome of which are creatures the best 

 fitted to withstand the struggle for existence, the most use- 

 ful in the scheme of nature, and the most in harmony with 

 the world about them. Progress, on the whole, therefore, 

 has been beneficent, the best proof of which is the last 

 [product of evolution, man, the paragon of creation. 



Lamarck laid the foundations of the doctrine of evolution, the fac- 

 tors he suggested being changes in the environment, inducing new needs 

 and desires in animals, and consequent use and disuse of organs, also 

 the transmission by heredity of characters acquired during the lifetime 

 of the individual. But his docfiues were published, in 1809. in very 

 crude shape, and before the sciences of geographical distribution, em- 

 bryology, palaeontology, and of histology -were adequately understood 

 or had even been founded. Lamarckism in its modern form is called 

 Neolamarckism. It comprises the fundamental factors of evolution. 



Darwin in 1859 published the principle of natural selection and its 

 .general application, and supported it upon such broad grounds that it 

 was universally accepted. Herbert Spencer insisted on the fact of 

 " the survival of the fittest." Neolamarckism endeavors to explain the 

 origin of variations, and thus lays the foundation on which natural 

 selection rests. 



We may with some changes adopt the following tabular view by 

 >Giard of the factors of organic evolution: 



{Direct. Changes of cosmical environment, changes of 

 climate, light, darkness, temperature, dryness and 

 humidity, physical and chemical constitution of the 

 p . soil and of waters, mechanical state of the milieu, 



", ni winds, currents of water, biological environment, 



food, parasitism, symbiosis. 



Indirect. Reaction against cosmical environmental 

 conditions; adaptation, convergence, reaction against 

 [ biological conditions, mimicry. 

 TT ,., , I Heredity, vital concurrence, natural and sexual selec- 

 11. beco aryl tion segregation, geographical isolation, amixia, 

 rs ' f hybridity. " 



