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SCIENCE 



[N. S. Vol. XL. No. 1026 



erally no doubt in the matter. "We have 

 pretty full histories of these crosses in 

 gladiolus, orchids, cineraria, begonia, cal- 

 ceolaria, pelargonium, etc. A very few 

 certainly arise from a single origin. The 

 sweet pea is the clearest case, and there are 

 others which I should name with hesita- 

 tion. The cyclamen is one of them, but 

 we know that efforts to cross cyclamens 

 were made early in the cultural history of 

 the plant, and they may very well have 

 been successful. Several plants for which 

 single origins are alleged, such as the Chi- 

 nese primrose, the dahlia and tobacco, came 

 to us in an already domesticated state, and 

 their origins remain altogether mysterious. 

 Formerly single origins were generally pre- 

 sumed, but at the present time numbers of 

 the chief products of domestication, dogs, 

 horses, cattle, sheep, poultry, wheat, oats, 

 rice, plums, cherries, have in turn been 

 accepted as " polyphyletie " or, in other 

 words, derived from several distinct forms. 

 The reason that has led to these judgments 

 is that the distinctions between the chief 

 varieties can be traced as far back as the 

 evidence reaches, and that these distinc- 

 tions are so great, so far transcending any- 

 thing that we actually know variation capa- 

 ble of effecting, that it seems pleasanter 

 to postpone the difficulty, relegating the 

 critical differentiation to some misty anti- 

 quity into which we shall not be asked to 

 penetrate. For it need scarcely be said that 

 this is mere procrastination. If the origin 

 of a form under domestication is hard to 

 imagine, it becomes no easier to conceive of 

 such enormous deviations from type com- 

 ing to pass in the wild state. Examine any 

 two thoroughly distinct species which meet 

 each other in their distribution, as, for in- 

 stances. Lychnis diurna and vespertina do. 

 In areas of overlap are many intermediate 

 forms. These used to be taken to be tran- 

 sitional steps, and the specific distinctness 



of vespertina and diurna was on that ac- 

 count questioned. Once it is known that 

 these supposed intergrades are merely mon- 

 grels between the two species the transi- 

 tion from one to the other is practically 

 beyond our powers of imagination to con- 

 ceive. If both these can survive, why has 

 their common parent perished*? Why when 

 they cross do they not reconstruct it instead 

 of producing partially sterile hybrids? I 

 take this example to show how entirely the 

 facts were formerly misinterpreted. 



When once the idea of a true-breeding — • 

 or, as we say, homozygous — type is grasped, 

 the problem of variation becomes an in- 

 sistent oppression. What can make such a 

 type vary? We know, of course, one way 

 by which novelty can be introduced — by 

 crossing. Cross two well-marked varieties 

 — for instance, of Chinese primiila — each 

 breeding true, and in the second genera- 

 tion by mere recombination of the various 

 factors which the two parental types sever- 

 ally introduced, there will be a profusion 

 of forms, utterly unlike each other, distinct 

 also from the original parents. Many of 

 these can be bred true, and if found wild 

 would certainly be described as good spe- 

 cies. Confronted by the difficulty I have 

 put before you, and contemplating such 

 amazing polymorphism in the second gen- 

 eration from a cross in Antirrhinum, Lotsy 

 has lately with great courage suggested to 

 us that all variation may be due to such 

 crossing. I do not disguise my sympathy 

 with this effort. After the blind compla- 

 cency of conventional evolutionists it is 

 refreshing to meet so frank an acknowledg- 

 ment of the hardness of the problem. 

 Lotsy 's utterance will at least do something 

 to expose the artificiality of systematic 

 zoology and botany. Whatever might or 

 might not be revealed by experimental 

 breeding, it is certain that without such 

 tests we are merely guessing when we pro- 



