BOOK REVIEWS. 



511 



the water crowfoot grows just as well, if not better, in the mud, but with 

 its stem and leaves in the air, now perfectly adapted to an aerial 

 existence. On the other hand, many xerophytes find their way into 

 marshes, &c, and change accordingly in a reverse way. The student 

 should look out for these interesting cases, for they point the way to 

 evolution itself. 



"Parallel Paths: a Study in Biology, Ethics, and Art." By T. W. 

 Eolleston. 8vo., 299 pp. (Duckworth, London, 1908). 5s. net. 



This book contains three parts. Part I. deals with the Argument 

 from Design, the Wheel of Life, De minimis, the Darwin-Lamarck, 

 the Darwin- Weismann, and the Directive Theory of Evolution. 

 Part II. discusses Law, Free Will, Personality, the Ethical Criterion 

 and Sanction. Part III. is on Art and Life. There are also four 

 appendices and an index. 



The author gives a good account of Paley's argument and of 

 Darwin's and Weismann 's position, showing clearly wherein they fail 

 to account for the cause of the origins of structure. He calls attention 

 to the invariable presence of "purpose," or, "as I should prefer to 

 call it, directivity.'" He does not add that this word is new to science — 

 having been invented by Professor A. H. Church, F.R.S.* Subsequently 

 he has a chapter on " Law and Directivity." This must be distinguished 

 from " force," for no force is self-directing. This is where Weismann 

 fails, for he says : " Life is merely a chemico-physical phenomenon." 

 It is more than force, for it is the director of all the forces in a living 

 body. 



The author is not quite correct in saying : " The variations on which 

 natural selection has to work are produced, according to Darwin, not 

 only by the exercise of particular organs, as in Lamarck's theory, but also 

 and more potently by " innate variations originating from unascertained 

 causes in the reproductive cells." The latter is Weismann's position; 

 but Darwin, in his "Animals and Plants under Domestication," f says it is 

 " changed conditions of life " in response to which " indefinite or definite 

 variations arise." Unfortunately for natural selection no indefinite 

 variations — i.e. a mixture of adaptive and inadaptive variations — have 

 ever been seen ; all the individuals of seedlings or animals grow in direct 

 adaptation — i.e. " definitely." 



The author says : " Stimulus and response, taken together, constitute 

 the directive force in obedience to which the world unfolds itself in the 

 evolutionary process." But no force can be "directive; " it is directed, 

 and by life. A man fires at a target ; the bullet hits it, not by any 

 "directive force," but by means of a force directed by the man. 



Another expression is very far from being correct : " Crystallization 

 is a process which trembles on the very verge of vital action." A crystal 

 can increase in size by superficial accretions of a like nature ; but a 

 living being grows by internal development. There is nothing in common 

 between them. 



* See " Directivity," an article in the Hibbcrt Journal, October 1907. 

 j- Vol. ii. p. 271. 



