REVIEWS 



Essays on Evolution, 1889-1907. By Edward Bagnall Poulton, D.Sc, 

 M.A., LL.D., F.R.S., etc., Hope Professor of Zoology in the University of 

 Oxford. [Pp. xlviii + 479.] (Clarendon Press, Oxford, 1908. Price 12s.) 



The first essay in this interesting volume asks whether the period of time supposed 

 to have elapsed since the earth cooled is long enough to allow of the whole 

 process of organic evolution at a rate consistent with Darwinism. The physicists 

 deal out the time, biologists have their views as to the rate of evolution ; do they 

 agree ? Prof. Poulton argues that the rate of progressive change was much 

 quicker in the higher grades of the animal kingdom, and he points out that 

 recent discoveries — such as that of radium — have made the physicists willing 

 to grant the biologists all the time they want. " Natural selection will never 

 be stifled in the Procrustean bed of insufficient geological time." 



The second essay seeks to answer the old conundrum, " What is a species ? " 

 and the solution offered is, " A synganic and synepigonic group of individuals," 

 that is to say, a group of individuals which can freely interbreed and are descended 

 from common ancestors. 



In the third essay Poulton contrasts in a most lucid way the Darwin-Wallace 

 theory of the natural selection of individual variations with the Lamarck-Spencer 

 theory of the inheritance of functional and environmental modifications ; in the 

 fourth essay — also a model of popular exposition — he states the pangenetic and 

 the germinal continuity theories of heredity. 



The fifth essay is of a kind which is particularly welcome ; it applies an 

 expert's knowledge of entomology to the question of the transmission of acquired 

 characters, and the conclusion is noteworthy : " When we bring together the 

 evidence supplied by the study of insects it is seen that it nowhere supports 

 the assumption upon which Lamarckian evolution is founded, the assumption 

 that acquired characters are transmissible by heredity." 



The next essay is a very interesting historical study dealing with James 

 Cowles Prichard's remarkable anticipations of modern views on evolution. In 

 the 1826 edition of his Researches into the Physical History of Mankind, Prichard 

 recognised the operation, though not the importance, of natural selection, and 

 pronounced against the transmission of acquired characters. Though he was 

 not quite consistent even at first, and certainly did not stick to his guns in 

 subsequent editions, he was " one of the most remarkable and clear-sighted of 

 the predecessors of Darwin and Wallace." In his hitherto unpublished Huxley 

 Lecture Poulton makes an interesting suggestion to explain why Huxley was 

 unable to feel much confidence in the theory of natural selection. It is the 

 experience of the student of living nature, he says, that inspires confidence in this 

 theory, and Huxley was not in the strict sense a naturalist. To use his son's 

 words, " It was the engineering side of nature, the unity of plan of animal con- 

 struction, worked out in infinitely varying detail, which engrossed him." 



The rest of the book is devoted to a discussion of mimicry and allied phenomena 



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