190 Lij'f and LvtUr* of Francis Gait on 



In (1) wp WN' that each cell had Ixsen an organic unit (quoad colour). In other words, the 

 Ktructuntl unit is identical with the organic unit. 



In ('.') the structural unit would not Ih! an urganic unit hut it would Ik.- an organic iiiclfcule. 

 It would liKve Ix-en due to the development, not of one geniniule hut of a gi-oup of geniiiiulee, 

 in which the hlnok and whiut K()ooieH would, on statistical grounds, lie equally numerous (as by 

 the hypothesis, they W(^n' equipotent). 



The larger the nuinljer of geniniules iu each organic molecule, the more uniform will the 

 tint of greyish l>e in the ditTerent unit« of 8t^lcturt^ it has lieen an old idea of mine, not yet 

 discarde<i and not yet worked out, that the nunib(;r of unilM in e^u^h molecule may admit of 

 being discovei-e*! by noting the relative numlM'r of case.s of each grade of deviation fi-om the 

 mean greyness. If then' wen> •_' gemnniles only, each of which niiglit Im- either white or black, 

 then in a large number of cases ont^qiiarter would always be quite wliiU;, one-quarter quite 

 black, aud one half would lie grey. If tlier»> were 3 molecules, we should have 4 grades of 

 colour (1 quite white, 3 light grey, 3 dark grey, 1 quite black and so on accoi-ding to the suc- 

 oeBsive lines of "Pascals triangle"). This way of l(K>king at the matter would pi'rhaps show 

 (a) whether the nuinlH*r in each given species of molecule was constant, and (6), if so, what those 

 numbers were'. Ever very faithfully yours, Francis Galton. 



42, Rutland Gate, Dec. 22/75. 



My dear Gkorge, I have never supposed otherwise than that the gemmules breed abun- 

 dautly all over the body, thougli I look upon them merely as local panisites, so to speak, that 

 live, multiply and die in great multitudes in the places where they are lodged, though occasion- 

 ally some of them may Ix' deUichwl and drifted along with the circulation, and so find their 

 way to the sexual eleinents — as was explained in the .seci>n<l part of the paper. 



It is by the itimiitlaiiff of all sorts of them, in every part of the Ixxly, that J accounted in 

 my |iaper for the reproduction of mutilated parts, and other .specilied phenomena, adding: "It 

 would much transa-nd my limits if I were to enter into these and kindred ({uestions, but it is 

 not neceiMuiry to do so, for it is sutticient to i-efer to Mr Darwin's work, where they are most 

 fully and carefully distrussed, and to consider while reading it whether the theory 1 have pro- 

 posed could not, as I think it might be, substituted with advantage for Pangeue^iis." 



[I have not the CtnUemporary Review by me and cannot give the Jiage of the extract. My 

 copy is merely a revise, paged from 1 onwards. It is in the 12th page of the revise.] 



In this passage, I meant to include propagation by buds. You will see in the preceding 

 page an allusion to the way in which the scattt^-etl alien germs "thrive and multiply." 



Now for the application of all this: wherever in a plant developed out of a bud or seedling, 

 (no matter which, for the 'stirp' is similar in Iwth cases) the alien, localised germs happen to 

 be congre^ted in sufficient number and varieties to form material for a fresh stirp, there will 

 be a tendency to produce a bud. Structural conditions, such as those found at the parts where 

 buds usually shoot, must of course Ije liel])ful in forwarding this tendency. 



The advantage of my theory ap]>ears to he this: — 



By Pangenesis, we should exjxsct lUl animals, however highly organised, to throw out buds. 



By my the<jry, I argue that where the animals are complex, the variety of germs concerned 

 in the making of them must be pro|K>rtionately gruit, and consequently the probability of a 

 complete set of them l)eing anywhere in existence, in the same immediate neighbourhood, is 

 diminished. Hence, the lower the organisation, the more freely does it bud and the higher onoe 

 do not bud, which is in accordance with fact. 



The budding, even of the higluwt animals in the embryonic stage, is intelligible by the joint 

 action of 3 causes sjiecial to that period : 



(1) The differentiation is less complete, and germs destined to be separated are then 

 together. 



(2) The embryo lieing small, the alien germs in separate structures are nearer than they 

 become afterwards. 



(3) The tissues are softer and afford less obstacle to the approach and aggregation of the 

 germs under their mutual athnities. 



' This letter shows how very closely Galton's thought at this time ran on Mendelian lines. 

 The paaMige should be taken in conjunction with that on p. 402 of the memoir on Blood-rela- 

 tionship. See our pp. 170-4 and compare p. 84. 



