A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. 



" To the solid ground 

 iKi- Of Nature trusts Die mind which bitilds for aye." — Wordsworth. 



THURSDAY, JULY 7, 1910. 



THE LAWS OF HEREDITY. 

 The Laws of Heredity. By G. Archdall Reid. With 

 a diagrammatic representation by Prof. H. H. 

 Turner. Pp. xi + 548. (London : Methuen and Co., 

 Ltd., 1910.) Price 21s. net. 



DR. ARCHDALL REID confesses that he is an 

 "extreme Darwinian." It is interesting that 

 ho has reached this position from the study of the 

 human species. He finds that this "vast field of re- 

 search has been left practical!^' untilled by students of 

 heredity." He is not, properly speaking, a naturalist ; 

 in fact, he has rather a poor opinion of naturalistic 

 work, and especially, I am sorry to say, of botanical. 

 This is the more remarkable as Darwin himself loved 

 ■ to exalt plants," and largely drew upon their study 

 for his theory. The author is, however, a physician 

 who, unlike most of his calling, is not satisfied with 

 being empirical. He finds himself "able to watch, 

 under conditions ensuring great accuracy, the 

 tremendous and crucial experiments made by nature." 

 With many of his results we are already familiar 

 from his previous writings. They are beginning to 

 obtain general acceptance; in proportion as they do 

 so, they must profoundly change our mode of dealing 

 with social problems of the utmost importance. 



The object of the present work is apparently to set 

 out the results of his investigations in a systematic 

 form, and to show that they can be exhibited as 

 deductions from widely accepted principles. The 

 method has undoubtedly the advantage that it has 

 enabled him to look at the whole subject from a new 

 point of view, and to bring a very acute criticism to 

 bear upon a good many questions on which opinion 

 at the moment is much divided. 



As Mill long ago pointed out, all science tends to 

 become deductive, and biology cannot be excluded. 

 But the progress which any particular science can 

 make in this direction altogether depends on the 

 certainty which attaches to the assumptions or pro- 

 positions with which we start. And where the 

 phenomena, as in the case of biology, are complicated 

 NO. 2123, VOL. 84] 



and obscure, the dil'ticulty must always arise as to 

 whether the proposition we start from is really ex- 

 I haustive of the fact. The validity of the conclusion 

 cannot exceed that of the premises. Lord Kelvin's 

 attempt to determine the age of the earth is an 

 example. The conditions of the problem have proved 

 to be insufficient, and I suppose no physicist would 

 now refuse an evolutionist a blank cheque as to time. 

 Darwin himself linked together a number of 

 separate inductions into a more comprehensive one 

 from which he then argued deductively. Dr. Archdall 

 Reid has continued the process, and in the first ten 

 chapters of his book has attempted a synthesis of 

 existing evolutionary theory. It is to be noted that 

 when this is done the order of exposition is rarely that 

 in which discovery was made. This is well known, 

 for example, to be the case with the text-book treat- 

 ment of the Newtonian theory. The process is, how- 

 ever, valuable, as it not merely brings to light a clear 

 chain of causation, but by vigorously testing the 

 strength of each link, often reveals unsuspected weak- 

 ness, and may even suggest new discovery. 



The author accepts and starts from Weismann's 

 theory of the continuity of the germ-plasm. From 

 this he makes the fundamental deduction that "indi- 

 viduals, for example, men, are nothing more than 

 dwellings which the germ-plasm builds about its 

 germinal descendants." Thence it follows "that the 

 child inherits nothing from his parent." What it 

 does inherit is nothing more than what was "inborn " 

 in the germ-plasm from which it started. The germ- 

 plasm, under the stimulus of nutrition, reproduces 

 itself, and also produces the enveloping soma. But 

 the latter also requires the stimulus of use (" injury " 

 may be regarded as use with a minus sign), as well 

 as that of nutrition : a limb will not reach full 

 development unless used, and mental powers will re- 

 main dormant unless exercised. But the characters 

 so developed are "rooted, as it were, in the germ- 

 plasm." They flow from it: the question which has 

 long divided biologists is whether modification of 

 those characters produced by the stimulus of use can 

 flow back and be transmitted to a succeeding genera- 

 tion. Darwin latterly apparently thought they could. 



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