May 22, 1919] 



NATURE 



225 



LETTERS TO THE EDITOR. 



'The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.] 



The Inheritance of Acquired Characters. 



Some years ago I directed attention {Eugenics Review, 

 lanuary, 1917. Transactions of the South-Eastern 

 Union of Scientific Societies, 19 17) to a remarkable 

 series of experiments by Kammerer, carried out in 

 "he Biologische Versuchs-anstalt, Vienna, the results 

 'if which were published in a number of papers ap- 

 pearing- in the Archiv fiir Entwicklungsmechanik. 

 in these experiments Kammerer subjected a number 

 of species of amphibia and reptiles to the action 

 of a modified environment throughout a period ex- 

 lending from their early youth until the attainment 

 of sexual maturity, and as a result modifications, 

 both of structure and habit, were produced. When 

 these altered individuals were allowed to pair and 

 produce young, these young: showed traces of the 

 influences to which their parents had been subjected 

 dn two ways, viz. (a) when they continued to live 

 in the same environment, the modifications of struc- 

 ture and habit which had appeared in the parents 

 reappeared in intensified form in the young; 

 ib) when they were transferred back to the original 

 environment proper to the species to which they 

 Ixdonged, they still showed, in their younger stages 

 of growtfi, some degree of the same change in habits 

 .and structure as the parents had exhibited. 



'I'hese results, as I pointed out, would, if con- 

 firmed, definitely establish the inheritability of ac- 

 ■quired characters, one of the most fundamental 

 ■questions in biology. But Kammerer 's results were 

 received by many of his zoological colleagues, not 

 only here, but also on the Continent, with a storm of 

 •criticism. Doubts were cast on his bona-fides, and 

 it became fashionable to ignore his results in dis- 

 cussing the laws of heredity. One of the most in- 

 teresting of Kammerer '$■ experiments had for its sub- 

 ject the " midwife toad " Alytes. This beast differs 

 from other toads, and, indeed, from the Anura in 

 general, in the circumstance that the sexes pair on 

 land, and not, as is the rule among Anura, in the 

 water. In all these water-breeding forms the male is 

 provided with a hornv patch situated on the hand 

 ijelow the index finger, in order to enable him to retain 

 his hold of the female when he clasps her under the 

 water. As all know, the eggs are fertilised after being 

 laid, and the young emerge as tadpoles provided with 

 three feathery external gills on each side of the head ; 

 but these gills become covered over by the growth of 

 an opercular fold from the hyoid arch and then 

 atrophy, and are functionally replaced by more in- 

 ternally situated gills. 



In Alytes the male is devoid of the horny patch 

 on the hand, as the skin of the female, being- com- 

 paratively dry, is sufficiently adhesive to allow him 

 to retain his hold without it. When the eg-gs are 

 laid — as is usual amongst toads, in long strings — the 

 male, after fertilising them, winds them round his 

 legs, and thus encumbered he lives in seclusion for 

 several weeks until the young are ready to hatch 

 out. He then visits the water, and the young- emerge 

 as advanced tadpoles, in which the external gills have 

 already been covered over. The eggs are fewer in 



number, much larger in size, and more abundantly 

 iprovided with yolk than those of other Anura. 



Now Kammerer states that if Alytes be kept under 



NO. 2586, VOL. 103] 



conditions of greater warmth than they are normally 

 accustomed to, they will live and flourish if provided 

 with a tank of water in which they can bathe if they 

 feel so inclined. In these circumstances they 

 begin to pair in the water, and the eggs slip off the 

 legs of the male and lie in the water. Most perish, 

 but, by keeping the water aseptic, a few will develop. 

 These, reared to maturity, produce, when sexually 

 ripe, more numerous eggs of smaller size than is 

 normal to the species, and the young hatch out at 

 an earlier stage of development. If we open the egg 

 of a normal Alytes, we discover that the embryo is 

 provided with only one external gill on each side. 

 Now in this F, generation the tadpoles emerge in this 

 stage, and Kammerer figures free-swimming tadpoles 

 of Alytes with one large external gill on each side. 

 When the F, tadpoles are reared to maturity, they 

 pair in the water and give rise to tadpoles with ihr9$ 

 external gills on each side, and these tadpoles, reared 

 to maturity, develop into males with a horny patch 

 on the finger. 



Concerning this experiment, our leading authority 

 on genetics. Prof. Bateson, thus speaks in his latest 

 book ("Problems of Genetics," p. 2or) :- " To my 

 mind this is the critical observation. If it can be 

 substantiated it would go far to proving Kammerer's 

 case. The figures which Kammerer gives [of the 

 horny patch : E. W. M.] are quite inadequate, and 

 as they merely indicate a dark patch on the thumbs, 

 it is not possible to form any opinion as to the 

 nature of the structure they represent. ... I wrote 

 to Dr. Kammerer in July, 1910, asking him for the 

 loan of such a sf>ecimen, and on visting the Bio- 

 logische Versuchs-anstalt in September of the same 

 year, I made the same request, but hitherto none have 

 been produced. " 



Now during the war it has been difficult to obtain 

 German scientific publications, but, through the kind 

 permission of the Board of Trade, we have been en- 

 abled to import all the numbers of the Archiv fiir 

 Entwicklungsmechanik published during the war. In 

 the latest of these, published in Berlin early in 

 the present year, there is a paper by Kammerer in 

 which he gives the results of further rearing of Alytes 

 under conditions of greater warmth than normal. His 

 original description of the horny patch on the hand 

 of the male was based on its appearance in males 

 of the F2 generation, but he describes now males of 

 the Fg generation, in which the horny patch is so 

 marked that its development exceeds that in the 

 normal male toad (Bufo). He gives photographs of 

 two Alytes males side by side, one of a normal male, 

 one of a modified male, and in this latter the homy 

 wart can clearly be made out. Further, he gives a 

 whole plate of figures of sections through the skin 

 of the hands of normal and modified males, and the 

 last show unequivocally the characteristic horny 

 papillae which make up the patch. 



jt must, we think, be conceded that Kammerer has 

 fairly taken up the gauntlet thrown down to him by 

 Prof. Bateson, and the present position of the matter 

 is that a strong prima-facie case for the inheritability 

 of acquired variations has been made out. Of course, 

 it is open to those who have attributed fraud to 

 Kammerer to assert that the whole of the evidence 

 adduced in this paper has been manufactured out of 

 whole-cloth, even though the photograph of the modi- 

 fied male is stated to have been taken by an .American 

 student in Vienna and not by Kammerer himself. 

 Such doubtinj; Thomases could be convinced onlv bv 

 a journey to Vienna and an inspection of the modified 

 males, for it is unreasonable to expect Kammerer 

 to send these priceless specimens to any zoologist who 

 chooses to doubt his word. It is to be hoped that. 



