NATURE 



THURSDAY, AUGUST i, 1907. 



ZOOLOGY AS AN EXPERIMENTAL SCIENCE. 



Experimental Zoology. By Prof. Thomas Hunt 

 Mortjan. Pp. xii + 454; illustrated. (New York: 

 The -Macmillan Company; London: Macmillan and 

 Co., Ltd., 1907.) Price u.v. net. 



THLS welcome book may be rejjarded as a landmark, 

 -ince it vindicates the position of zoology as an 

 experimental science. It is the modern successor of 

 .Semper's famous " .\ninial Life," and it has had its 

 forerunners in various smaller books, such as De 

 Varigny's "Experimental Evolution." But it is, we 

 believe, the first scholarly and critical review of a 

 ' large part of the enormous mass of experimental 

 investigations which have been a feature of zoological 

 science during the last fifteen years. Thus it gives 

 the student a comprehensive and orderly survey (with 

 well-selected bibliography) of a widely-scattered scien- 

 tific literature; it enables him rapidly to bring himself 

 up to date as regards experiments on the influence of 

 environment, on hybridising, on inbreeding, on the con- 

 ditions of growth and reproduction, on the determin- 

 ation of ;ex, and so on ; and the data are presented in 

 a manner so critical and stimulating that the book is 

 bound to have a great influence in promoting experi- 

 mental research, which is likely to be prominent in 

 zoological laboratories for centuries to come. For 

 " while the historical study of zoology must always 

 remain .a legitimate field for activity, as human history 

 has been a time-honoured study, there can be little 

 doubt that the more promising and searching method 

 of zoological study in the future will be found in 

 experiment." 



To have furthered this movement is sure to be the 

 reward of Prof. Morgan's book, which is at once a 

 careful balance-sheet of past results and an incentive 

 to add to them. The author has made all zoologists 

 his debtors, for the work is uncommonly well done. 

 It is an interesting sign of the times that the author 

 is " professor of experimental zoology " in one of the 

 leading universities of the world. 



The author's general point of view is thus indi- 

 cated : — 



" The branches of biology that have made most 

 extensive use of the experimental method are physi- 

 ologv, bacteriologv, and physiological chemistry. 

 The zoologist and the embryologist have also to deal 

 with phvsiological problems, and already the begin- 

 ning of important experimental work has been carried 

 out in this field; but the most distinctive problem of 

 zoolofiical work is the change in form that animals 

 undergo, both in the course of their development from 

 the egg (embryology) atid in their development in 

 time (evolution)." 



It is to an examination of the experimental study of 

 these changes in form thai the book is mainly de- 

 voted. 



" Experimental morphology would perhaps nearly 

 indicate the field to be examined; but since the line 

 between experimental physiology and experimental 

 morphology is often hard to draw, and since I shall 

 not hesitate at times to enter upon the physiological 

 side of manv problem', I have chosen the somewhat 



NO, T970. VOL. 76] 



broader title of Experimental Zoology to include the 

 subjects to be treated." 



The principal topics discussed fall under six head- 

 ings : — evolution, growth, grafting, the influence of 

 the environment on the life-cycle, the determination of 

 sex, and the secondary sexual characters; and if 

 there are any zoologists who have not been following 

 the recent development of experimental work, they will 

 be amazed at the amount of profoundly interesting 

 work that has already been done. New vistas are being 

 opened out on all sides, and zoology is entering upon 

 a fresh and most promising phase. It should be noted, 

 too. (hat Prof. Morgan tells his tale in a style so 

 lucid and graphic that even the uninitiated cannot fail 

 to follow what is certainly one of the most fascinating 

 zoological books ever published. 



The main theme of the book is " the central problem 

 of morphology — the causes of ihe changes in form, or 

 at least the determination of the conditions under 

 which changes in form occur." It must be noted, 

 however, as the author is well aware, that the title 

 " Experimental Zoology " is much wider than the 

 contents of the book. He has deliberately refrained 

 from discussing, (a) recent experimental work on the 

 psychical aspects of vital phenomena as dealt with 

 in recent works by Loeb, Lloyd Morgan, Jennings, 

 Bethe, and others ; (6) the study of regeneration (to 

 which he devotcj a previous excellent treatise); and 

 (c) experimental embryology, which has also received 

 comprehensive treatment in more than one recent 

 volume. The exclusion of the last-named department 

 is especially regrettable, though it is ungracious to say 

 so. For, after all, the central problem of morphology 

 is not so much concerned with the environnienlal 

 production of modifications, or with the Mendelian 

 phenomena of inheritance, or with the determination 

 of sex, but with morphogenesis. Thus a treatise on 

 experimental zoology which refrains from a thorough- 

 going discussion of the fundamental researches of men 

 like Roux and Wilson, Driesch and Herbst, illustrates 

 what the experimentalists have called "autotomy." 

 Let us hope that in subsequent editions the missing 

 parts — absolutely necessary to completeness — may be 

 regenerated. The author's competence to secure this 

 is well known. Of course, a book should always be 

 received with due consideration of the author's aim 

 and prescribed limits, and what we have ventured to 

 say is in no sense intended as criticism, but we may 

 further remark that under the title of " Experimental 

 Zoology " we may justly include not only experiments 

 bearing on morphogenesis (individual and racial), but 

 also those which enable us better to understand the 

 daily life of the fully formed creature. Much of the 

 work that has been done in comparative physiology 

 and psychology is definitely experimental, and just as 

 essential to an all-round outlook as the work of 

 Mendel and de Vries. 



It is of course impossible to give a summary of 

 the author's conclusions, but we may give two or 

 three samples. 



" The experimental evidence in favour of the inherit- 

 ance of acquired characters is unsatisfactory." " Used 

 with discretion Mendel's law may still unlock many 



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