August 19, 1910] 



SCIENCE 



243 



lations of the " sex-chromosomes " without 

 assuming alternative male and female genes. 

 It was pointed out that each of the two sug- 

 gested interpretations included or involved 

 " assumptions which without additional data 

 must be considered as serious difficulties. . . . 

 Additional data will therefore be required, I 

 think, to show in what measure either of the 

 two general interpretations that have been 

 considered may approach the truth" (p. 38). 

 In view of so explicit a statement of my posi- 

 tion it is rather astonishing to learn from a 

 recent publication' that in my third " Study," 

 because of the difficulties of the second inter- 

 pretation, I " maintain the alternative view, 

 that the allosomes have qualitative differences 

 that are sex-determining, with Mendelian 

 dominance, and with selective fertilization " 

 (p. 3). It is equally disconcerting to read, 

 further on, that " Boveri, in opposition to 

 Wilson's explanation, does not believe that 

 one chromosome has a male and the other a 

 female tendency, but that they differ only in 

 activity" (p. 5). There is here no indication 

 of the fact that the view opposed by Boveri to 

 mine is also mine, having been put forward 

 as a part of my second interpretation (!). 



Not until three years after my third 

 " Study " did I take a more definite position 

 in regard to this question, and then one de- 

 cidedly against selective fertilization. In the 

 fourth " Study " (1909, sent to press in Feb- 

 ruary, 1908) it was stated only that the first 

 interpretation " should not be rejected without 

 further data, and especially not until the 

 question of selective fertilization has been 

 put to the test of direct experiment" (p. 97). 

 In the fifth " Study " (1909) this question is 

 not taken up. Finally, in two general re- 

 views of the whole subject in its broader bear- 

 ings' selective fertilization is treated as so 

 improbable as almost to invalidate any inter- 

 pretation into which it enters. I am there- 

 fore again somewhat at a loss to comprehend 

 how another recent writer can say that after 

 framing several theories of sex I have at 



'Montgomery, Biol. Bull., XIX., 1. 1910. 



■ Science, February, 1909 ; Science Progress, 

 April, 1910. 



length adopted as my " latest view " one that 

 " not only assumes a great complication of 

 gametic representatives, but also involves 

 selective fertilization."^ 



I am very willing to take whatever may be 

 my just share of blame for such misunder- 

 standing — even though I think it might have 

 been avoided by a little more care in reading. 

 It may be due partly to the fact that I did not 

 at first see that my second (quantitative) in- 

 terpretation was no less Mendelian than the 

 first, as Castle has since pointed out. Beyond 

 this, a certain ambiguity may have been 

 caused by too great brevity in certain pas- 

 sages of the fourth and fifth " Studies," where 

 the question of qualitative differences of the 

 '• sex-chromosomes " is touched upon. These 

 brief references took for granted the context 

 supplied by the full critical discussion given 

 in the third " Study," and the ambiguity dis- 

 appears, I think, when this is borne in mind. 

 One instance may be given from the fifth 

 " Study," which contains the statement, " I 

 believe that if the idiochromosomes be the sex- 

 determinants their difference is probably a 

 qualitative one" (p. 189). In this passage the 

 careless omission of the words " in the male " 

 after " difference " obscures the meaning and 

 might readily mislead a reader who had not 

 the full context in mind. No ambiguity will 

 be found, I hope, in the two reviews already 

 cited, where the general conclusions from my 

 own and other investigations in this field are 

 brought together. 



Lastly, I have not committed myself to the 

 view that the " sex-chromosomes " represent 

 the exclusive factors of sex-determination, 

 though in several places they have been pro- 

 visionally assumed to be such in order to dis- 

 cover the consequences of such a view. Other 

 possibilities are pointed out in several of my 

 papers on the subject, and I have gone no 

 farther than to maintain the probability that 

 these chromosomes are " one of the essential 

 factors." This question, like that of selective 

 fertilization, seems to me an open one; and 

 until both questions have received a certain 



= Geoffrey Smith, Q. J. M. S., February, 1910. 



