776 



NA TURE 



[June 17, 1922 



states that we have absolute certainty that new forms 

 of Ufe, new orders and new species, have arisen on the 

 earth. The explanation is the difficulty, but we have 

 ample evidence that organisms, whatever their 

 characters, are only produced by reproduction from 

 parents. 



One is tempted to conclude that Mr. Bateson 

 attaches some mystical meaning to the word " species." 

 He says we have no reason to suppose that any 

 accumulation of characters of the same order as those 

 met with in genetical experiments would culminate in 

 the production of distinct species. According to him 

 there is some underlying base which is specifically 

 distinct and bears the characters. I fail to see that 

 this idea has any scientific meaning or validity. 

 What is this base ? In science we must regard 

 things and phenomena objectively. We distinguish 

 species by characters, just as we distinguish all objects 

 by their qualities. For example, we have the 

 familiar example of single comb and rose comb in 

 fowls. We cannot have singleness and rose-ness 

 without the comb that exhibits these characters. If 

 they occurred in nature, excluding crossing or 

 hybridisation, they would be specific characters, at 

 least in company with other differences they might 

 be. Is the comb then the base ? The comb must 

 have some character and shape, and thus we cannot 

 have the comb without a character. We can have 

 the entire absence of comb, as in the allied genus 

 Phasianus ; and so with all other characters. This 

 idea of a specific base distinct from specific characters 

 seems merely false metaphysics. How can we con- 

 ceive of an organism without characters, or characters 

 without an organism ? Perhaps Mr. Bateson means 

 that unit characters such as those which can be 

 transferred in Mendelian crosses might all be taken 

 away, and still an organism would be left with non- 

 Mendelian characters. What are these characters ? 

 He does not tell us. We have cases of the absence of 

 pigment in, e.g., a bird, then the feathers are left. We 

 may have an organism without feathers, and then the 

 skin is left. We can scarcely have an organism, at 

 any rate a vertebrate, without a skin. On the other 

 hand, we may have factors, whatever their nature, 

 which in the absence of one or more other factors 

 produce no visible character, as in the cases of white 

 varieties of animals and plants which, when bred 

 together, produce coloured offspring. It has been 

 shown that there are several kinds of white varieties 

 or races, the distinguishing characters of which are 

 invisible. Perhaps Mr. Bateson means that species 

 were originally distinct in this way, separated by 

 characters which were non-apparent. 



Mr. Bateson insists on the rarity of the occurrence 

 of new dominants under observation in experimental 

 breeding, although new recessives, that is, the loss of 

 particular characters from a combination, are common 

 enough. Even in Drosophila few new dominants 

 have been seen, and none of these could be expected 

 to survive under natural conditions. He further 

 states that in tracing the origin of our domesticated 

 animals and plants we can scarcely ever point to a 

 single wild species as the probable progenitor. Now 

 it seems to me that there is' very good evidence that 

 all our breeds of domesticated fowls have descended 

 from Gallus bankiva, and in the numerous existing 

 breeds there are many dominant characters which 

 are not present in the wild ancestral form, e.g. the 

 dominant white of the White Leghorn, and the rose 

 comb. Mr. Bateson says he cannot imagine such a 

 new dominant character being produced. But surely 

 it is evident that they have been produced in the 

 succession of generations of domestic fowls. Mr. 

 Bateson's difficulty seems to be merely that w^e do 

 not know how they came into existence. We can, 



NO. 2746, VOL. 109] 



however, scientifically form the conclusion that they 

 originate by some change or development in the 

 chromosomes, not directly dependent on any corre- 

 sponding external stimulus. 



Another reason which Mr. Bateson gives for his 

 scepticism is that the chief attribute of species is that 

 the product of their crosses is frequently sterile. 

 This seems on the face of it illogical. If the sterility 

 is only frequent it follows that there are many cases 

 in which such sterility is absent. In that case, as 

 there are many species which produce fertile off- 

 spring, the sterility of species hybrids cannot be the 

 " chief attribute " of species. It is neither a universal 

 nor necessary characteristic, and all we can say is 

 that we do not know how it arises in certain cases. 

 John C. Phillips in America crossed three wild species 

 of duck {Anas boscas, A. tristis, and Dafila acuta) and 

 found the progeny fertile. Bonhote has published 

 the results of numerous similar experiments in this 

 country. The various species of Bovidae also are 

 stated to be fertile inter se. 



I find it very difficult to understand Mr. Bateson's 

 reasoning on this subject. He states in one place 

 that the fact that hybrids between species are by no 

 means always sterile is a commonplace of everyday 

 experience, and then a little farther on, insists that 

 until the production is witnessed of an indubitably 

 sterile hybrid from completely fertile parents which 

 have arisen from a single common origin, we have no 

 acceptable account of the origin of " species." The 

 two statements contradict each other. Interspecific 

 sterility may be very mysterious, but it has nothing 

 to do with the origin of these species which do not 

 exhibit this sterility. Moreover, there is evidence of 

 the occurrence under observation and experiment of 

 new varieties which are more or less infertile with 

 one another. Oenothera gigas, a mutant from O. 

 Lamarckiana, shows a great degree of sterility when 

 crossed with other mutants from the same species, 

 and two mutants of Drosophila in Morgan's experi- 

 ments are almost completely sterile with one another. 



It is not very surprising that genetical researches 

 of the Mendelian kind have not thrown much light 

 on the occurrence of variations and mutations, for 

 except in the cases of OEnothera and Drosophila they 

 have usually consisted in analysing by crossing 

 experiments the hereditary factors already present, 

 instead of breeding many generations from a single 

 form and studying the variations that occur. To my 

 own mind, there is no proof that the numerous breeds 

 and varieties of domestic fowls, all descended almost 

 certainly from the single species Gallus bankiva, differ 

 in their essential nature from groups of closely allied 

 species and varieties in a natural state. 



The feeling, however, that chiefly prompts me to 

 comment upon Mr. Bateson's Toronto address is one 

 of protest against the implied disparagement of those 

 who have not ceased to discuss evolution. There is 

 more in evolution than the origin of species. Mr. 

 Bateson himself has contributed largely to the proof 

 that the distinctions between species have little or 

 nothing to do with adaptation, but at the same time 

 he has failed to realise the true nature and importance 

 of adaptation in itself. In his address he makes no 

 reference at all to adaptation, or to the relation 

 which it bears to recapitulation in ontogeny, one of 

 these " academic problems of morphology " which were 

 discussed with such avidity when both he and I were 

 young, and which he relegates with such confident 

 assurance to the limbo of obsolete things. Yet he 

 writes of the older time : " Regardless of the obvious 

 consideration that ' modification by descent ' must be a 

 chemical process, and that of the principles governing 

 that chemistr^^ science had neither hint nor surmise 

 nor even an empirical observation of its working." 



