DARWINISM DEFENDED. 157 



to account for the steadily progressive tendency of life as a 

 whole without calling to its aid any unknown and doubtful 

 perfecting principle. 



"To summarise : Natural selection, acting on the whole 

 organism, tends to produce more and more definite tend- 

 encies in all surviving forms of life, which tendencies are 

 progressive and continuous in character. Variable condi- 

 tions, by partially altering the line of selection, induce a 

 temporary indefiniteness. And lastly, the process of selec- 

 tion being itself able to be the indirect, though not the direct, 

 cause of those favourable variations, which it subsequently 

 selects from, is able to dispense with any subsidiary factors, 

 provided it has a certain number of elementary properties 

 of life which afford sufficient material to work with." 



APPENDIX. 



1 Semper, Carl, "Der Haeckelismus in der Zoologie," 1876. 



2 In 1876, Gustav Jaeger anticipated Weismann's later much- 

 heralded theory of the continuity of the germ-plasm in his 

 "Zoologische Briefen." 



3 For an excellent detailed critical account of these general, as 

 well as the several accessory theories (amphimixis, polar bodies, 

 etc.) of Weismann, see Romanes's "An Examination of Weismann- 

 ism," 1893. 



4 It is of interest to note that the strongest defenders of neo- 

 Darwinism to-day are the English naturalists. Americans mostly 

 lean toward neo-Lamarckism ; the Germans are divided. 



5 Plate, Ludwig, "Uber die Bedeutung des Darwin'schen Selec- 

 tionsprinzip und Probleme der Artbildung," 2d ed., 1903. 



6 Prof. Weldon, an English Darwinian, has recorded {Nature, 

 Sept. 22, 1898) an extremely interesting and much discussed statis- 

 tical and experimental study of the presumable action of natural 

 selection working on slight fluctuating quantitative variations. "I 

 can only attempt to discuss," says Prof. Weldon, "the importance 

 of small variations, and the rate of organic change, in the one case 

 which I happen to know. The particular case I have myself studied 

 is the variation in the fronta.1 breadth of Carcinus mamas [a small 

 shore-crab]. 



