NATURE 



'3 [ 



THURSDAY, APRIL 10, 191 



THE HERITABLE RESULTS OF CHANGED 



NURTURE. 

 Das Problem dcr Vercrbung " enuorbener Eigen- 



schaften." By R. Semon. Pp. viii + 203. 



(Leipzig : Wilhelm Engelmann, 1912.) Price 



3.20 marks. 



RETURNING to the much-discussed question 

 of the transmission of acquired characters, 

 Prof. Richard Semon goes over the whole ground. 

 Conclusions — both affirmative and negative — have 

 been based on certain sets of data, but all the facts 

 must be faced if we are to form a sound judg- 

 ment. This is indeed what many biologists have 

 tried to do. The first chapter, which is historical, 

 includes the commendable suggestion that it 

 is time to stop using inexact terms like 

 " Lamarckism," so often taken as synonymous 

 with the theory of the transmission of acquired 

 modifications. In the second chapter the author 

 formulates the question at issue : A stimulus sets 

 up an excitation in a parental body ; the residual 

 effect of this excitation is a change in the reaction- 

 capacity (an " Engramm ") ; can we say that in 

 favourable circumstances there results a change 

 in the heredit.irv potency of the germ-cells, and of 

 such a nature that the offspring show a change 

 in the same direction as that exhibited in the 

 parent? 



Prof. Semon begins his survey of the evidence 

 by considering language, acquired knowledge, and 

 training ; and while he does not claim to prove 

 anything, he refers to cases which suggest that 

 individual experience must count somehow. Why 

 is it, for instance, that a young buzzard, taken 

 from the nest, treats an adder quite differently 

 from a grass-snake? Has experience not counted 

 at all in the evolution of this inborn power of dis- 

 crimination? The fourth chapter brings together 

 numerous interesting cases which suggest the 

 inheritance of engramms. Young acacias with an 

 "inherited disposition" to a certain rhythm of 

 sleeping and waking will, as it were, try to give 

 expression to this in quite unnatural conditions of 

 illumination and darkness. Braus has shown that 

 if the fore-limb be removed from the larva of a 

 Bombinator, the operculum still shows the thin 

 area, usually with a small hole, through which the 

 limb would press out if it were there. Is this not 

 a reminiscence of a previously established 

 " mechanomorphosis " ? The degeneration of the 

 eyes of cave animals, considered in detail and in 

 connection with Kammerer's experiments on 

 Proteus, point to a hereditary accumulation of the 

 structural results of disuse and darkness. In 

 NO. 2267, VOL. gi] 



regard to this and similar cases it appears to us 

 to remain a question of interpretation. Which 

 reading of the facts presents least difficulty ? 



Prof. Semon does not think that we should give 

 up expecting a specific hereditary result of often- 

 repeated injuries, and he refers, for instance, to 

 Kammerer's experiment on the Ascidian, Ciona 

 intestinalis, the siphons of which were cut off over 

 and over again. In consequence of the stimulus, 

 the length of the regenerated siphons was exces- 

 sive, and the uninjured offspring had also exces- 

 sively elongated siphons. We must, of course, 

 hear more about this interesting case. The sixth 

 chapter marshals the positive evidence which goes 

 to show that parents much modified by peculiari- 

 ties of nurture may have offspring changed in the 

 same direction, although the peculiar nurture is no 

 longer operative. The evidence includes recent 

 observations on the acclimatisation of plants, 

 Woltereck's experiments on the helmet of 

 Daphnia, and Kammerer's striking work on 

 salamanders and the nurse-frog. 



The question then arises : How are the germ- 

 cells affected? Prof. Tower was led by his well- 

 known experiments on potato-beetles to the view 

 that the environmental factors operated on the 

 germ-cells without any induction from the un- 

 changed soma of the parent. But Prof. Semon 

 points out that an adult beetle could not be ex- 

 pected to show much external change, and argues 

 that there is no escape from a theory of somatic 

 induction, the various possible modes of which 

 are carefully and acutely discussed. The author 

 concludes that long-continued functional modifica- 

 tions may by somatic induction exert a specific 

 effect on the germ-cells, and that certain environ- 

 mental stimuli may also affect the germ-cells by 

 somatic induction. The results depend on three 

 variables : the nature, strength, and duration of 

 the excitations, the general constitution of the 

 organism, and the state of the germ-cells — sus- 

 ceptible or otherwise — at the time. Prof. Semon's 

 latest presentation of the case for the heritability 

 of somatogenic changes is a valuable contribution 

 to aetiology, and one that must be reckoned with 

 by all biologists. The book is written with force 

 and clearness and in admirable scientific temper. 



J. A. T. 



THE WORK OF G. YON REICHENBACH. 

 Deuts'ches Museum Lebensbeschreibungen und 

 Urkunden. Georg von Reichenbach. By 

 Walther v. Dyck. Pp. iii+140 + viii plates. 

 (Munich : Deutsches Museum, 1912.) 



DURING the last eight or nine years an 

 extremely instructive and valuable collec- 

 tion illustrating the various sections of science and 



G 



