902 REPORT— 1898. 



I hope I have convinced you that the law of chance enables one to express easily 

 and simply the frequency of variations among animals ; and 1 hope 1 have con- 

 vinced you that the action of Natm-al Selection upon such fortuitous variations can 

 be experimentally measured, at least in the only case in which anyone has attempted 

 to measure it. I hope I have convinced you that the process of evolution is some- 

 times so rapid that it can be observed in the space of a very few years. 



I would urge upon you in conclusion the necessity of extending as widely as 

 possible this kind of numerical study. The whole difficulty of the theory of 

 Natural Selection is a quantitative difficulty. It is the difficulty of believing that 

 in any given case a small deviation from tlie mean character wiU be sufficiently 

 useful or sufficiently harmful to matter. That is a difficulty which can only be got rid 

 of by determining in a number of cases how much a given variation does matter ; 

 and I hope I have shown you that such determination is possible, and, if it be 

 possible, it is our duty to make it. 



We ought to know numerically, in a large number of cases, how much varia- 

 tion is occurring now in animals ; we ought to know numerically how much effect 

 that variation has upon the death-rate ; and we ought to know numerically how 

 much of such variation is inherited from generation to generation. The labours of 

 Mr. Gal ton and of Professor Pearson have given us the means of obtaining this 

 knowledge, and I would urge upon you the necessity of obtaining it. For 

 numerical knowledge of this kind is the only ultimate test of the theory of Natural 

 Selection, or of any other theory of any natural process whatever. 



The Biological Exhibition at the Zoological Gardens was opened by the Right 

 Hon. Sir John Lubbock, M.P., D.C.L., F.R.S. 



FRIDAY, SEPTEMBER 9. 



The following Papers and Reports were read : — 



1. The Proof obtained by Guy A. K. Marshall that Precis octavia-nata- 

 censis and P. sesamus are seasonal forms of the same species. By 

 Professor E. B. Poulton, M.A., F.R.S. 



2. Photographic Records of Pedigree Stock. 

 By Francis Galton, M.A., F.R.S. — See Reports, p. 597. 



3. Preliminary Note on the Races and Migrations of the Mackerel {Scomber 

 scomber). By Walter Garstang, M.A., Naturalist in charge of 

 Fishery Investigations under the Marine Biological Association; late 

 Fellow of Lincoln College, Oxford. 



The present note contains the principal results of an attempt to determine 

 whether there are any racial peculiarities in groups of mackerel taken in different 

 localities. Such peculiarities have not hitherto been recognised, even as between 

 American and British representatives of the species ; but it is clear that the 

 establishment of such peculiarities would affect to a considerable degree our ideas 

 concerning the migrations of this fish. 



During the past year I have determined the peculiarities of more than 1,600 

 mackerel in regard to 10 chosen characters. Of these fi^h, 100 were obtained 

 *t Newport, R.I., U.S.A., and were forwarded to me through the friendly agency 



