592 



NA TURE 



[February 27, 1908 



Mr. Cunningham says (p. 367) that my article was as 

 dogmatic as it could possibly be. It was meant to be. 

 It was meant to stir up those who continue to use the 

 old terms " acquired " and " innate " without really 

 bothering much about their signification. It has achieved 

 its object admirably. 



He also says that I assert that there "is no sense in 

 the distinction between acquired characters and innate 

 ones with regard to inheritance " [which I did not say], 

 " that all characters are both acquired and innate " 

 [which I did] ; he continues : — " This in the accepted 

 meaning of the words is simply untrue." Well, of course 

 it is. My point was that the accepted meaning of the 

 terms was vague, that it had led to confusion, and that 

 it ought to be dropped. 



Mr. Cunningham does not follow me. I am willing 

 to admit that that may be my fault. I fully recognise, 

 as he does, that the characters of organisms may be 

 divided into two big categories, which have for a long 

 time been called " acquired " and " innate." But I hold 

 that the difference between these two classes of characters 

 is very inadequately expressed by the terms " acquired " 

 and " innate," and that a much better, though, of course, 

 provisional, classification of characters is into (a) those 

 which owe their existence to the interaction between some 

 innate factor and the stimulus (for want of a better term) 

 of nutrition, and (b) those which owe their existence to 

 the interaction between some innate factor and the stimulus 

 of use or injury. 



The view that all characters are acquired during 

 ontogeny as the result of a definite stimulus acting on an 

 innate factor was expressed by Weldon (Biometrika, 

 vol. i., p. 367), who has also described {loc. cil.) how he 

 succeeded in preventing the appearance of the amnion in 

 the hen's egg by withholding the necessary stimulus. 



A full answer to Mr. Cunningham's letter is quite out 

 of the question, because it would involve a discussion on 

 all the meanings of the terms " innate " and " acquired " 

 and a history of their use, which could not be compressed 

 within the limits of a single number of Nature. But 

 reference must be made to one of the things " innate," 

 as opposed to acquired, certainly does not mean. What- 

 ever it means, it does not mean what it literally means. 

 It does not mean the kind of character one is born with. 

 Before it was known that all organisms develop from a 

 single eel! it may have meant that, but now that we 

 know that they do, we regard classifications of characters 

 into those which appear before the act which separates 

 intra-uterine from extra-uterine, and those which appear 

 after it, as interesting from a historical point of view 

 only. Yet in this year 1908 we actually read in a letter 

 to Nature (I am not quoting from memory) that a Negro 

 " is brown (not black) when he is born ; that is an innate 

 character." The facts are true, of course, but not 

 relevant. The fact that a negro is brown when he happens 

 to be born does not matter. The fact we have to face 

 is that the ovum which gave rise to Booker T. Washington 

 was probably not browner than that which gave rise to 

 Oeorge. The statement that the colour of the former is 

 innate does not in the least help us to understand the 

 causes to which the difference between the colours of the 

 two men is due. A. D. D. 



TFuRTHER space cannot be devoted to this correspondence. 

 — Kd.I 



The Possibility of Life in Mars. 



The perseverance with which Prof. Lowell has prosecuted 

 his investigation of the surface markings of Mars compels 

 admiration ; the evidence he has brought forward for the 

 objective reality of much of the detail he has shown in 

 his sketches serves to convince many reluctant minds ; but 

 the interpretation he has put upon these markings, in 

 terms of phenomena associated with life as we know 

 it on our own planet, requires stronger evidence than he has 

 yet brought forward in view of the considerations that 

 follow. 



The blue-green coloration he attributes to vegetation ; 

 its change to chocolate-brown to the fading of verdure with 

 the change in the season. If we grant that the conditions 

 on Mars have been possibly such as to allow of the develop- 



NO. 2000, VOL. y/"] 



ment of living organisms from inorganic matter, is it 

 likely that the course of evolution has been so exactly 

 similar to that on the earth that a chlorophyll-bearing 

 organism has resulted? Like conditions produce like 

 results — granted ; but when one considers the quasi- 

 fortuitous nature of the conditions determining the 

 characters of those organisms that survive in the process 

 of evolution, the remoteness of the probability that the 

 development of the power of forming chlorophyll should 

 happen twice, in two independent evolutionary systems, 

 seems overwhelming. 



Again, Prof. Lowell attributes the markings which he 

 considers irrigation systems to intelligent beings. it is 

 possible that that high degree of adaptability to environ- 

 ment, which we call intelligence, might have evolved 

 independently on two planets, but it seems in a very high 

 degree improbable. 



Similarly, other points in his scheme of interpretation 

 may be conceivable, but highly improbable. But the 

 probability of the whole is the continued product of all 

 the independent probabilities ! The evidence, then, in 

 favour of Prof. Lowell's views will require to be of a 

 much more overwhelming character to claim the assent of 

 those who appreciate their extreme improbability. 



Opposition to the views of Prof. Lowell has generally 

 been based on difficulties regarding the physical condition 

 of Mars. It is the object of this letter to emphasise the 

 far greater improbabilities involved in the biological 

 aspect. 



Prof. Lowell attributes the reluctance of many to accept 

 his position to the emotions of men. I venture to think 

 that emotions are in his favour ; it is the human desire 

 for an anthropomorphic interpretation of nature — in this 

 case perhaps one should rather say a geomorphic interpre- 

 tation — that has prompted his views, and but for which they 

 would receive small consideration. C. O. Bartrum. 



12 Heath Mansions, N.W., February 17. 



In Dr. William Lockyer's review of Dr. Russel 

 Wallace's book on the habitability of Mars he refers to 

 Dr. Johnstone Stoney's contention that aqueous vapour 

 cannot exist on a planet of that size because the velocity 

 of the molecules would be too great for its attraction to 

 retain them. I do not know what temperature was 

 assumed in the calculation, but a dozen miles above the 

 surface of the planet the temperature of its atmosphere 

 must approach absolute zero — a condition of things in 

 which even hydrogen would not have the necessary 

 velocity to escape. 



The question is an important one for those who are 

 interested in the history of the earth, for, whether we 

 choose the nebular or planetesimal view of its origin, there 

 must have been a time when the attraction it exercised on 

 the outer portion of its atmosphere was far less than at 

 present, and if Dr. Johnstone Stoney were right ther= 

 would be some difficulty in understanding how any watp- 

 vapour remained. J. W. Evans. 



Imperial Institute, S.W., February 15. 



The Stresses in Masonry Darrs. 



Prof. Pearson's letter in Nature of February 20 

 requires little in the way of reply from me, since my 

 essential point is now admitted, viz. that the stresses xx 

 and £s are practically the same in a slab, whether it be 

 free or form part of a complete dam. I should, however, 

 like to point out to Prof. Pearson, re his comparison 

 between a parabola and an equivalent sine curve, that at 

 5° the ordinate is only one-twelfth the maximum ordinate, 

 so that an error of 30 per cent, in this ordinate is one of 

 but 2i per cent, on the maximum, which would be, accord- 

 ingly, absolutely negligible in practical engineering. As 

 regards the remainder of his letter, engineers have the 

 support of many eminent elasticians in their refusal to 

 accept his and .St. Venant's dictum that the maximum 

 stretch is the proper criterion of the safety of a structure. 

 In any. case, the true criterion is a question for the engineer 

 and the physicist, and not for the mathematician. The 

 most recent experiments, I may add, negative Prof. 

 Pearson's views on this head. H. M. Martin. 



83 St. James's Road, Croydon. 



