54 THE PLAY OF ANIMALS. 



number who believe in the "all-sufficiency of natural 

 selection." Leaving out of the question the fact that 

 our knowledge of phylogenesis rests finally on the mys- 

 terious ocean of metaphysical problems, of which I have 

 spoken, it is by no means settled, even in the sphere of 

 empirical science, that selection of ordinary individual 

 variation suffices to bring about, even gradually and by 

 minute degrees, a change from one species to another. 

 There are those who deny this, to whom the Darwinian 

 system is comparatively insignificant. As in surging 

 water the particles of each wave move both backward 

 and forward, so that the surface motion forward is really 

 only apparent, so the selection of hereditary qualities 

 can not extend beyond a certain definite point, and 

 for the transformation to new species other and essen- 

 tially different variations are necessary, in their opin- 

 ion, in the structure of the germ substance itself.* 



Nevertheless, we know no principle except that of 

 selection, and we must go as far as that will take us. 

 Absolute knowledge of such phenomena is practically 

 unattainable, f 



* Thus Galton and Bateson. F. Galton, Discontinuity in Evo- 

 lution, Mind, 1894. 



f Since this was written a new theory has been proposed which 

 is evidently well adapted to supplement the selection principle. 

 Baldwin has discovered a way whereby natural selection is fur- 

 thered by individual accommodations or functional adaptations, and 

 directed by them without the assumption of any direct inheritance 

 of acquired characters ; as he says " the appearance of such inherit- 

 ance will be fully explained " (Mental Development in the Child and 

 the Race, German translation, p. 188, fourth English edition, chap, 

 vii, § 4). [Cf. The Psychological Review, vol. iv, p. 394 f., July, 1897. 

 This influence is called by him " organic selection ".] Independ- 

 ently of Baldwin, Osborn and Lloyd Morgan have reached a simi- 

 lar position. [It is also now accepted by Mr. Alfred Russel Wallace 

 and Prof. E. B. Poulton, of Oxford. The latter says (Science, New 



