June 14, 1888] 



NA TURE 



157 



little. Each addition to the neck so acquired was trans- 

 mitted to the descendant, and by accumulation of the 

 changes thus produced the modern long-necked condition 

 was attained. According to Weismann, what happens 

 is this. In each generation slight variations in the length 

 of the neck, as in the other parts of the body, occur. 

 These variations are due to constitutional causes which 

 are transmitted. When greater length of neck became 

 important to the animal, those animals with necks a little 

 longer or capable of being stretched out a little further, 

 would have the advantage, would survive longer, and 

 leave more offspring. The offspring, inheriting the 

 constitution of their parents, would inherit this tendency 

 to have longer necks. By the continual elimination in 

 many generations of the short-necked forms, and by the 

 seizing hold of each naturally-occurring variation, the long- 

 necked condition would finally appear. 



As variations are constantly occurring, natural selection 

 must constantly be at work to maintain the standard of 

 any organ. Whenever an organ ceases to be of use, or even 

 when it becomes merely of subordinate utility, this selective 

 maintenance falls into abeyance. A state that Weismann 

 calls Panmixia results. Variations below the standard 

 cease to be eliminated, and the organ slowly degenerates. 

 In this way is explained degeneration through disuse : 

 degeneration from conditions that are not harmful but 

 merely unnecessary. In many cases organs that are not 

 used degenerate very much during individual lives, but 

 this occurs through failure of nutrition. Weismann 

 believes such effects not to be transmitted. Were these 

 effects inherited, useless organs must inevitably disappear 

 very much more rapidly and completely than there is 

 evidence for. 



Instincts are elaborated, not by the accumulation of 

 transmitted individual experience, but by continual selec- 

 tion of mental variations in the required direction. For 

 instance, the instinct to avoid enemies arose not by 

 accumulation of experience, for experience of the incon- 

 venience of being devoured could hardly be transmitted, 

 but by the naturally more timid forms surviving, and 

 leaving more offspring than their less wary brethren. 



Talent and even genius often run through several 

 generations ; and certainly mental powers can be much 

 increased in individual lives. But the exhibition of talent 

 and genius depends on a combination of many physical 

 and mental conditions in which constitutional variation is 

 ever present, and these variations are undoubtedly 

 inheritable. Moreover, the history of families of con- 

 spicuous ability (as, for instance, that of the musical family 

 Bach) shows that the highest development often occurs in 

 the middle of the series, while the theory of the trans- 

 mission of acquired characters would demand to find it 

 at the end. 



Selection of variations best explains cases of adaptation 

 to new climates. But the immense influence of climate 

 conditions on nutrition in each ontogeny must be taken 

 into account. 



Qualitative changes at first present some difficulty, but 

 it must be remembered that qualitative changes are nearly 

 always at bottom quantitative. A surface appears naked, 

 though covered with many small hairs ; or light-coloured, 

 though scattered pigment-cells are present. Quantitative 

 variations in such conditions certainly occur, and are 

 certainly transmitted, and natural selection can readily 

 change the number or size of hairs or pigment-cells, and 

 produce so-called qualitative results. 



It is not claimed as yet that the inheritance of acquired 

 characters can be excluded in every case. But increasing 

 knowledge of the conditions of life and of the functions 

 of organs causes ever a larger and larger part of the 

 phenomena of the organic world to be explained by the 

 selection of naturally-arising variations. 



P. Chalmers Mitchell. 



IMPERIAL GEOLOGICAL UNION. 



"D EFERRING to my letter on the above subject, 

 -t^- published in Nature, vol. xxxvi. p. 146, I beg to 

 communicate, for the information of those interested in 

 the matter, the substance of a report made to the Royal 

 Society of Canada at its meeting on May 22, in 

 Ottawa. 



The Committee reported that it had, as directed, 

 printed the letter of Sir William Dawson to the President 

 of the Royal Society, and the first report of the Com- 

 mittee, and had circulated these extensively, sending them 

 especially to geologists and Societies in Great Britain 

 and the colonies and dependencies of the Empire. A 

 large number of replies had been received, testifying to 

 a somewhat general wish for union and co-operation. 



The matter was then laid before the Council of the 

 Royal Society, with the view of holding a Conference in 

 London under its auspices. The subject was taken up 

 by the Council in October last, and a resolution was 

 passed and communicated to the Committee to the effect 

 that, having regard to the existing condition of the 

 question of scientific federation, and the various con- 

 tingencies that may occur during the next few years, they 

 do not see their way to summon such a Conference as 

 that recommended. 



In view of this resolution it was felt to be useless for 

 the present to attempt any farther action. Still, as the 

 desire for and appreciation of the benefits of the union 

 contemplated seemed to be very general, and as oppor- 

 tunities may occur later for giving it a practical form, it 

 was thought best by the Royal Society of Canada to con- 

 tinue its Committee, with power to correspond with other 

 bodies and with persons interested. The undersigned 

 will therefore be glad to receive any communications on 

 the subject. 



Some misconception appears to exist as to the relations 

 of the intended movement to the International Geological 

 Congress which is to meet in London in September next. 

 They have in reality no connection, except that, 

 under certain contingencies, they might be mutually 

 helpful. 



A Union of British Geologists might exercise an in- 

 fluence for good in connection with the plans for unifica- 

 tion of classification, nomenclature, and mapping, which 

 have occupied the attention of the Congress ; but its 

 function would rather be the positive one of uniting 

 workers throughout the wide area occupied by the British 

 Empire, and enabling them more effectually to co-operate 

 in the extension of actual knowledge, in giving mutual 

 aid, in enlarging the mental vision of local and special 

 workers, in making accessible to isolated labourers the 

 common stock of knowledge, and in preventing the inter- 

 ference and discordance which result from disunited 

 effort. 



That there are difficulties in the way of the realization 

 of such apian as applied to British and colonial geologists 

 in the first instance, and ultimately to all English-speaking 

 geologists, there can be no doubt ; but they are continually 

 diminishing, in consequence of greater facilities for inter- 

 course and the rapid growth of scientific work in the 

 various outlying parts of the Empire. The idea is thus a 

 fruitful one, certain to be realized in the future ; and 

 possible even at present if a central nucleus could be 

 secured for an Imperial organization. It is not impossible 

 that the large gathering of English-speaking geologists 

 in London in September may afford opportunity for 

 further discussion of the plan ; and if the invitation which 

 it is understood will be given by our friends of the United 

 States to hold the next meeting in America be accepted, 

 this may constitute another step in the same direction. 



Montreal, May 31. 



J. Wm. Dawson. 



