September 22, 1898] 



NA TURE 



499 



executive committee, and the local officers. He said 

 that the great success of the meeting was largely due to 

 the efforts of those referred to in the resolution. Never 

 before in his experience of the Association had local 

 effort led to such absolute smoothness in the working of 

 the machine. It was a pity that the work of the Associa- 

 tion had been so hard as to prevent many members from 

 seeing all the points of interest in this interesting city of 

 Bristol. The magnificent educational establishments 

 which crowded the city were themselves worthy of close 

 attention, and at some future meeting the Ikitish Associa- 

 tion might find Ikistol at the head of some great south- 

 western University. 



Prof Schjifer seconded the resolution. 



Mr. James Scott (of Toronto), on behalf of the Canadian 

 members, expressed high appreciation of the welcome 

 which had been accorded to them. 



The resolution was then carried with much enthusiasm. 



The Mayor of Bristol, Mr. Howell Davis (chairman 

 of the executive committee), Mr. Arrowsmith (local 

 treasurer), and Mr. Arthur Lee and Dr. Bertram Rogers 

 (local secretaries), each responded, Mr. Arrowsmith ex- 

 pressing his acknowledgments for the cheque for 120/. 

 which had been given by the Council of the Association 

 towards the Colston Hall fund. 



Prof Riicker next moved a comprehensive vote of 

 thanks to all public bodies and private persons who had 

 contributed to the success of the meeting. He said that 

 if the citizens of Bristol had not supported the local 

 officers, the success of the meeting could not have been 

 secured in so large a measure. As President of the 

 International Committee of the Magnetic Conference, 

 he was charged to convey the best thanks of the foreign 

 members to the Association and to the local authorities 

 for the extreme kindness of their reception. 



Dr. Gladstone seconded the resolution, which was 

 carried unanimously, the High Sheriff responding. 



Sir John Evans moved a cordial vote of thanks to Sir 

 William Crookes, President, for his admirable address 

 and for his conduct in the chair. He prophesied, when 

 introducing Sir William to the chair, that the Association 

 would hear from him a remarkable address, and that 

 prophecy had been amply justified. One of the most 

 valuable portions of that address was that in which 

 public attention was called to the fact that there was in 

 our atmosphere an inexhaustible supply of nitrogen, and 

 that means should be discovered for employing that 

 nitrogen to increase the produce of the earth. Sir 

 William Crookes had fulfilled with courtesy and dis- 

 tinction all the many and various duties which the past 

 week had imposed upon him, and the thanks of the 

 Association were cordially due to him. 



Prof Roberts-Austen seconded the resolution, which 

 was carried with enthusiasm. 



Sir W. Crookes, in responding, said that he felt like an 

 electrical switch-board — for really he was only the trans- 

 mitter and distributor of these thanks to those whose 

 help had been so material. He was especially grateful to 

 the Mayor and Mayoress, whose hospitality had facili- 

 tated his work so greatly ; and he regarded as one of the 

 highest compliments ever paid to him the invitation to 

 the remarkable smoking-symposium of the previous 

 Friday evening. As for the President's office, the pace 

 was getting too fast for human endurance ; and in a short 

 time the British Association would, if the vvork were to 

 be got through at all, have to elect a young athletic man 

 of five-and-twenty instead of a man over three-score years 

 and ten. 



Prof Riicker announced that the number of tickets 

 issued for the present meeting of the Association was 

 2446. 



This concluded the proceedings. The next meeting will 

 be held at Dover, and will commence on September 13, 

 1899. 



NO. 1508, VOL. 58] 



SECTION D. 



ZOOLOGY. 



Opening Address by Prof. W. F. R. Weldon, M.A., 

 F.R.S., President of the Section. 



In attempting to choose the subject of the address with which 

 custom obliges your president to trouble you, I felt that I should 

 have the best hope of interesting you if I decided to speak to 

 you on the subject most interesting to myself. I therefore pro- 

 pose to discuss, as well as I can, the principal objections which 

 are urged against the theory of Natural Selection, and to 

 describe the way in which I think these objections may be met. 



The theory of Natural Selection is a theory of the importance 

 of differences between individual animals. In the form m which 

 Darwin stated it, the theory asserts that the smallest observable 

 variation may affect an animal's chance of survival, and it 

 further asserts that the magnitude of such variations, and the 

 frequency with which they occur, is governed by the law of 

 chance. 



Three principal objections are constantly brought forward 

 against this theory. The first is that the species of animals 

 which we know fall into orderly series, and that purely for- 

 tuitous variations cannot be supposed to afford opportunity for 

 the selection of such orderly series ; so that many persons 

 feel that if the existing animals are the result of selection 

 among the variable offspring of ancestral creatures, the vari- 

 ations on which the process of Natural Selection had to act 

 must have been produced by something which was not chance. 



The second objection is that minute structural variations can- 

 not in fact be supposed to affect the death-rate so much as the 

 theory requires that they should. And it is especially urged 

 that many of the characters, by which species are distinguished, 

 appear to us so small and useless that they cannot be supposed 

 to affect the chance of survival at all. 



The third objection is that the process of evolution by Natural 

 Selection is so slow that the time required for its operation is 

 longer than the extreme limit of time given by estimates of the 

 age of the earth. 



Now the first of these three objections, the objection to for- 

 tuitous variation as the source of material on which Natural 

 Selection can act, is very largely due to a misunderstanding of 

 the meaning of words. The meaning of the word Chance is so 

 thoroughly misunderstood by a number of writers on evolution 

 that I make no apology for asking you to consider what it 

 does mean. 



Consider a case of an event which happens by chance. Sup- 

 pose I toss a penny, and let it fall on the table. You will agree 

 that the face of the penny which looks upwards is determined by 

 chance, and that with a symmetrical penny it is an even chance 

 whether the "head" face or the "tail" face lies uppermost. 

 For the moment, that is all one can say about the result. Now 

 compare this with the statements we can make about other 

 moving bodies. You will find it stated, in any almanac, that 

 there will be a total eclipse of the moon on December 27, and 

 that the eclipse will become total at Greenwich at 10.57 p.m. ; 

 and I imagine you will all feel sure, on reading that statement, 

 that when December 27 comes the eclipse will occur ; and it 

 will become total at 10.57 p.m. It will not become total at 

 10.50 p.m., and it will not wait until ii.o p.m. You will say, 

 therefore, that eclipses of the moon do not occur by chance. 



What is the difference between these two events, of which we 

 say that one happens by chance, and the other does not ? The 

 difference is simply a difference of degree in our knowledge of 

 the conditions. The laws of motion are as true of moving pence 

 as they are of moving planets ; but it happens that we know so 

 much about the sun, and the earth, and the moon, that we know 

 the circumstances which affect their relative positions very 

 accurately indeed ; so that we can predict withm less than a 

 minute the time at which the shadow of the earth will next fall 

 upon the moon. 



But the result of tossing a penny depends upon a very large 

 number of things which we do not know. It depends on the 

 shape and mass of the penny, its velocity and direction when it 

 leaves one's hand, its rate of rotation, the distance of one's hand 

 from the table, and so on. If we knew all these things before 

 tossing the penny, we should be able to predict in each case 

 what the result would be, and we should cease to regard pitch 

 and toss as a game of chance. 



As it i.s, all we know about these complicated conditions is 

 that if we toss a penny for a number of times, the conditions 



