4o8 



NA TURE 



[August 25, 1904 



individual which in a few generations gave rise to the 

 Shirleys. Many a black Amphidasys betuiaria may have 

 emerged before, some sixty years ago, in the urban con- 

 ditions of Manchester the black var. doubledayaria found 

 its chance, soon practically superseding the type in its place 

 of origin, extending itself over England, and reappearing 

 even in Belgium and Germany. 



Darwin gave us sound teaching when he compared man's 

 selective operations with those of Nature. Yet how many 

 who are ready to expound Nature's methods have been at 

 the pains to see how man really proceeds? To the domesti- 

 cated form our fashions are what environmental exigency 

 is to the wild. For years the conventional Chinese primrose 

 threw sporadic plants of the loose-growing stellata variety, 

 promptly extirpated because repugnant to mid-Victorian 

 primness. But when taste, as we say, revived, the graceful 

 Star Primula was saved by Messrs. Sutton, and a stock 

 raised which is now of the highest fashion. I dare assert 

 that few botanists meeting P. stellata in Nature would 

 hesitate to declare it a good species. This and the Shirleys 

 precisely illustrate the procedure of the raiser of novelties. 

 His operations start from a definite beginning. As in the 

 case of P. stellata, he may notice a mutational form thrown 

 off perfect from the start, or, as in the Shirleys, what 

 catches his attention may be the first indication of that flaw 

 which if allowed to extend will split the type into a host 

 of new varieties each with its own peculiarities and physio- 

 logical constitution. 



Let anyone who doubts this try what he can do by selec- 

 tion without such a definite beginning. Let him try from 

 a pure strain of black and vifhite rats to raise a white one 

 by breeding from the whitest, or a black one by choosing 

 the blackest. Let him try to raise a dwarf (" Cupid ") 

 sweet pea from a tall race by choosing the shortest, or a 

 crested fowl by choosing the birds with most, feather on 

 their heads. To formulate such suggestions is to expose 

 their foolishness. 



The creature is beheld to be very good after, not before 

 its creation. Our domesticated races are sometimes re- 

 presented as so many incarnations of the breeder's prophetic 

 fancy. But except in recombinations of pre-existing 

 characters — now a comprehensible process — and in such 

 intensifications and such finishing touches as involve 

 variations which analogy makes probable, the part played 

 by prophecy is small. Variation leads ; the breeder follows. 

 The breeder's method is to notice a desirable novelty, and 

 to work up a stock of it, picking up other novelties in his 

 course — for these genetic disturbances often spread — and we 

 may rest assured the method of Nature is not very different. 



The popular belief that evolution, whether natural or 

 artificial, is effected by mass-selection of impalpable differ- 

 ences arises from many errors which are all phases of one 

 — imperfect analysis — though the source of the error differs 

 with the circumstances of its exponent. When the scientific 

 advocate professes that he has statistical proofs of the con- 

 tinuity of variation, he is usually availing himself of that 

 comprehensive use of the term Variation to which I have 

 referred. Statistical indications of such continuity are 

 commonly derived from the study, not of nascent varieties, 

 but of the fluctuations to which all normal populations are 

 subject. Truly varying material needs care in its collection, 

 and if found is often sporadic or in some other way un- 

 suitable for statistical treatment. Sometimes it happens 

 that the two phenomena are studied together in inextricable 

 entanglement, and the resulting impression is a blur. 



But when a practical man, describing his own experience, 

 declares that the creation of his new breed has been a verv 

 long affair, the man of science, feeling that he has found 

 a favourable witness, puts forward this testimonv as con- 

 clusive. But on cross-examination it appears that the 

 immense period deposed to seldom goes back beyond the 

 time of the witness's grandfather, covering, say, seventy 

 years ; more often ten, or eight, or even five years will be 

 found to have accomplished most of the business. Next, 

 in this period — which, if we take it at seventy years, is a 

 mere point of time compared with the epochs of which the 

 selectionist discourses — a momentous transformation has 

 often been effected, not in one character but many. Good 

 characters have been added, it may be, of form, fertility, 

 precocity, colour, and other physiological attributes, un- 

 desirable qualities have been eliminated, and all sorts of 



defects " rogued " out. On analysis these operations can 

 be proved to depend on a dozen discontinuities. Be it, more- 

 over, remembered that within this period, besides producing 

 his mutational character and combining it with other 

 characters (or it may be groups of characters), the breeder 

 has been working up a stock, reproducing in quantity that 

 quality which first caught his attention, thus converting, if 

 you will, a phenomenon of individuals into a phenomenon 

 of a mass, to the future mystification of the careless. 



Operating among such phenomena the gross statistical 

 method is a misleading instrument ; and, applied to these 

 intricate discriminations, the imposing Correlation Table 

 into which the biometrical Procrustes fits his arrays of 

 unanalysed data is still no substitute for the common sieve 

 of a trained judgment. For nothing but minute analysis 

 of the facts by an observer thoroughly conversant with the 

 particular plant or animal, its habits and properties, checked 

 by the test of crucial experiment, can disentangle the truth. 



To prove the reality of Selection as a factor in evolution 

 is, as I have said, a work of supererogation. ■ With more 

 profit may experiments be employed in defining the limits 

 of what Selection can accomplish. For whenever we can 

 advance no further by Selection, we strike that hard outline 

 fixed by the natural properties of organisms. We come 

 upon these limits in various unexpected places, and to the 

 naturalist ignorant of breeding nothing can be more 

 surprising or instructive. 



Whatever be the mode of origin of new types, no 

 theoretical evolutionist doubts that Selection will enable him 

 to fix his character when obtained. Let him put his faith 

 into practice. Let him set about breeding canaries to win 

 in the class for Clear Yellow Norwich at the Crystal Palace 

 Show. Being a selectionist, his plan will be to pick up 

 winning yellow cocks and hens at shows and breed them 

 together. The results will be disappointing. Not getting 

 what he wants, he may buy still better clear yellows and 

 work them in, and so on until his funds are exhausted, but 

 he will pretty certainly breed no winner, be he never so 

 skilful. For no selection of winning yellows will make 

 them into a breed. They must be formed afresh by various 

 combinations of colours appropriately crossed and worked 

 up. Though breeders differ as to the system of combin- 

 ations to be followed, all would agree that selection of birds 

 representing the winning type was a sure way to fail. The 

 same is true for nearly all canary colours except in Lizards, 

 and, 1 believe, for some pigeon and poultry colours also. 



Let this scientific fancier now go to the Palace Poultry 

 Show and buy the winning Brown Leghorn cock and hen, 

 breed from them, and send up the result of such a mating 

 vear after vear. His chance of a winner is not quite, but 

 almost, nil. For in its wisdom the fancy has chosen one 

 tvpe for the cock and another for the hen. They belong to 

 distinct strains. The hen corresponding to the winning 

 cock is too bright, and the cock corresponding to the winning 

 hen is too dull for the judge's taste. The same is the case 

 in nearly every breed where the sex-colours differ markedly. 

 Rarely winners of both sexes have come in one strain — a 

 phenomenon I cannot now discuss — but the contrary is the 

 rule. Does anyone suppose that this system of " double 

 mating " would be followed, with all the cost and trouble 

 it involves, if Selection could compress the two strains into 

 one? Yet current theory makes demands on Selection to 

 which this is nothing. 



The tyro has confidence in the power of Selection to fix 

 type, but he never stops to consider what fixation precisely 

 means. Yet a simple experiment will tell him. He may go 

 to a great show and claim the best pair of Andalusian fowls 

 for any number of guineas. When he breeds from them 

 he finds, to his disgust, that only about half their chickens, 

 or slightly more, come blue at all, the rest being blacks or 

 splashed whites. Indignantly, perhaps, he will complain to 

 the vendor 'that he has been supplied with no selected breed, 

 but worthless mongrels. In reply he may learn that beyond 

 a doubt his birds come from blues only in the direct line 

 for an indefinite number of generations, and that to throw 

 blacks and splashed whites is the inalienable property of 

 blue Andalusians. But now let him breed from his 

 " wasters," and he will find that the extracted blacks are 

 pure and give blacks only, that the splashed whites similarly 

 give only whites or splashed whites — but if the two sorts 

 of " wasters " are crossed together blues oiilv will result. 



NO. I 8 17, VOL. 70] 



