November 24, 192 1] 



NATURE 



401 



addressed to Dr. J. H. Gilbert, and dated "Down, 

 February i6, 1876," The following passage is the one 

 which interests us here : — 



"It is admitted by all naturalists that no problem 

 is so perplexing as what causes every cultivated plant 

 to vary, and no experiments as yet tried have thrown 

 any light on the subject. Now for the last ten years 

 I have been experimenting in crossing and self- 

 fertilising plants ; and one indirect result has surprised 

 me much, namely, that by taking pains to cultivate 

 plants in pots under glass during several successive 

 generations, under nearly similar conditions, and by 

 self-fertilising them in each generation the colour of 

 the flower often changes, and, what is very remark- 

 able, they became in some of the most variable 

 -pecies, such as Mimulus, Carnation, etc., quite con- 

 stant, like those of a wild species." 



We now know that the colour changes and the 

 becoming constant to which Darwin refers were the 

 results of the repeated self-fertilisation of heterozygous 

 material, so that the supposed variability evidently 

 was nothing but segregation after a cross. 

 ' Velp, Holland, November 2. J. P. Lotsy. 



It would take too much space to reply in detail to 

 all of Dr. Lotsy's statements, for which I have great 

 respect. They go far outside the original point at 

 issue, but it is necessar\' to refer to the more important 

 of them, and it will then probablv be seen that the 

 others are immaterial. In his original letter (Nature, 

 October 27, p. 274), which commented on an article 

 of mine on " British Roses and Hybridity " (Nature, 

 September 15, p. 99), he states that Jeffrey's work 

 tends " to show that the presence of * bad pollen ' is 

 proof [my italics] of a hybrid origin," and goes on to 

 say that this view is "much strengthened " bv other 

 work. He correctly states that I took exception to 

 that view, my own view being that "bad pollen " is 

 unsafe as a criterion of hybridity, in support of which 

 I cited various facts. As some of these facts were 

 from a paper of which I was joint author, the original 

 article was unsigned, but since this controversy, which 

 was not of my seeking, has arisen, I prefer to sign 

 my own name. In his present letter Dr. Lotsy seems 

 to forget that the burden of proof rests upon those 

 who assume that bad pollen is a proof of hybridity. 

 He says that my postscript to his article is "not 

 according to facts," and that he did not suggest the 

 hybrid nature of Trillium, Dirca, and Scoliopus. I 

 can only ask, if that is the case, why did he refer to 

 them in his original article? Cvtological work, which 

 is by no means all "recent," proves that hybridity 

 is a cause of bad pollen, but bv no means proves that 

 it is the only cause. 



Dr. Lotsv has apparently omitted a considera- 

 tion of lethal factors from his views. This is a 

 more recent discovery which is of much signifi- 

 cance in the interpretation of sterility, not only in 

 Drosophila, but in various CEnothera forms, and it 

 may apply either to gametes or zygotes. The con- 

 ception has already been fruitfullv applied, not onlv to 

 various plants and animals, but also to man himself. 

 When I said that the theorv of mutation requires the 

 occurrence of a certain proportion of defective germ- 

 cells I had similar cases in mind, and did not mean 

 to imply that mutations were necessarilv always 

 accompanied by germ-cell sterility. But clearly, if 

 lethal factors account for germ-cell sterility in some 

 cases, it is inadmissible to assume that bad pollen is 

 in itself a proof of hybridity. We must apply the 

 conception of multiple causes. 



It follows that in any given case, such as that of 

 Oenothera Latnarckiana, bad pollen mav have 

 originated from crossing, from lethal factors, or from 

 NO. 2717, VOL. 108] 



some other cause, unless one or more of these possible 

 causes can be eliminated. Dr. Lotsy says, "We now 

 know that O. Laniarckiana is a hybrid." One can 

 only ask how we know, and in what sense he is using 

 the term hybrid. So far as the theory of mutation in 

 Oenothera is concerned, it no longer matters whether 

 O. Laniarckiana is a garden hybrid or not, since the 

 work of Bartlett has proved that various close- 

 pollinated wild .American species of CEnothera show 

 the same mutation behaviour. 



Finally, I would say that if by his theon,- of evolu- 

 tion by hybridisation Dr. Lotsy means merely that 

 the intercrossing of related races is the condition in 

 which evolution has frequently taken place, I, for 

 one, would heartily agree with him. For I have long 

 advocated the view that among open-pollinated plants 

 and most animals the evolutionary unit is an inter- 

 breeding population of closely related forms. I fancy 

 many biologists adhere to a similar point of view. 

 But I take it that Dr. Lotsy means much more than 

 that by his theor}*, and if I understand him correctly, 

 that is his reason for tacitly denying the existence of 

 germinal changes. One can only ask how two visibly 

 similar homozygous organisms when crossed can give 

 rise to new germinal characters if they have not 

 during the previous period of their isolation under- 

 gone germinal changes. R. Ruggles G.\tes. 



King's College, Strand, November 11. 



Biological Terminology. 



(a) "Varlation is the sole cause of non-inherit- 

 ance "; (b) "."Apart from variations like exactly begets 

 like, when parent and child develop under like con- 

 ditions " ; (c) " The development of the individual is 

 a recapitulation (with additions and subtractions due 

 to variations) of the evolution of the race." Here are 

 three statements which seem to me "tn effect " iden- 

 tical. To Dr. Bather the first two seem identical, 

 but not the third. But if the child in his own de- 

 velopment step by step recapitulates (with variations) 

 the development of the parent, and the parent in the 

 same way recapitulated that of the grandparent, and 

 so on to the beginning, how, in the world, can the 

 development of the individual be anything other than 

 a recapitulation (with the accumulated variations) of 

 the evolution of the race? If that be so, does not 

 (b) necessarily involve (c)? (c) is merely (6) applied 

 to a succession of parents and children. Dr. Bather 

 says (Nature, October 27, p. 271) that this is not 

 what biologists mean. Then what do they mean? 

 ■ Recapitulation " must be one of those terrible words 

 which, like "inherit," are used, quite unconsciously, 

 with a number of diverse and even contradictcMy 

 meanings. 



It is pleasant to find that Dr. Bather approves of 

 Prof. Goodrich's address, for probably it has set the 

 heather alight at last. In my humble way I also 

 am enormously pleased. Still, Dr. Bather should 

 bear in mind the history of this matter, some of which 

 Prof. Goodrich indicates. As long ago as the 

 'eighties Weismann declared that " an organism can- 

 not acquire anything unless it already possesses the 

 predisposition to acquire it." At that time, too, 

 doctors were beginning to insist that not actual 

 diseases, but only predispositions to acquire them, 

 were inheritable. Weismann failed to perceive the 

 necessarv- consequences of his own idea — predisposi- 

 tion is all that can be inherited in the case of any 

 character; all characters, therefore, are equally and 

 in exactly the same sense innate, acquired, and inherit- 

 able. Instead he assumed, with Lamarck, that some 

 characters are innate -and others acquired, and so 

 started the famous — or infamous — Lamarckian con- 

 troversv. Sandeman did, however, verv definitely 



