February 3, 192 1] 



NATURE 



719 



The Determination of Sex. 



Mechanxsmus und Physiologic der Geschlechts- 

 bestimmung. By Prof. Richard Goldschmidt. 

 Pp. viii + 251'." (Berlin: Gebriider Borntraeger, 

 1920.) Price 32 marks. 



THOUGH Prof. Goldschmidt 's treatise on sex- 

 determination is in scope similar to the text- 

 ' books published by Doncaster and by Morgan in 

 191 2, knowledge has increased so rapidly since 

 I hen that there is plenty of room for a new state- 

 ment. Moreover, as the author has himself de- 

 voted several years to the study of a special case 

 wliich departs from the ordinary rules, his views 

 will be of interest to geneticists. Up to a point, 

 the mechanism of sex-determination is clear. On 

 the one hand, we know that in several birds and 

 ,mc Lcpidoptera the female is heterozygous in 

 cx, but we have equally sound proof that in man 

 and in several insects other than Lepidoptera the 

 condition is reversed, the female being homo- 

 zygous and the male heterozygous in respect 

 of the .sex-factor. The evidence for these con- 

 clusions is mainly either genetical or cytological. 

 With the exception of Drosophila, which, after 

 some doubt, observers have agreed to regard as 

 having the male XY and the female XX, there 

 is no specific form in which positive evidence of 

 both kinds, genetical as well as cytological, can 

 1 yet be produced. The absence, however, of such 

 . convergent testimony need not trouble us at this 

 stage, for each cla.ss of proof is by itself adequate 

 so far as it goes. On the whole, also, though 

 difliculties are met with in special examples, the 

 evidence from operative and other collateral ob- 

 servations agrees well with the conclusions de- 

 ll duccd from genetical and cytological sources. 



Sex being, then, decided by the contribution 

 which one or other of the gametes makes to the 

 offspring, how shall we account for cases in which 

 these seemingly predetermined consequences can 

 by interferences of various kinds be disturbed? 

 Evidence of this description falls into several 

 cla.sses, and its consideration forms a chief pur- 

 pose of the present book. Hitherto the most 

 famous is that provided by R. Hertwig's experi- 

 ments on frogs. By delaying fertilisation, he 

 found that the proportion of males could be 

 greatly increased. The suggestion that the 

 females had died off was shown to be inapplicable, 

 and there .seemed to Ik- no escape from the con- 

 clusion that eggs which in the ordinary course 

 would have become females did after, and pre- 

 sumably because of the delay in fertilisation, be- 

 come males. The fact, however, that the matura- 

 ition-divisions in the case of the frog occur after 

 NO. 2675, VOL. 106] 



the eggs are laid offered, as Hertwig pointed out, 

 a possible, if rather unlikely, solution; for the 

 artificial delay might have some influence in de- 

 ciding which elements should be extruded in the 

 polar bodies, and thus the sex-ratio might be dis- 

 turbed. (Juite recently Seiler, a colleague of Prof. 

 Goldschmidt's, claims to have actually witnessed 

 consequences of this kind following upon the 

 introduction of special conditions in the case of 

 the Psychid moth Talaeporia, and to have ob- 

 tained cytological evidence that a rise of tempera- 

 ture during the reduction-division caused the X- 

 chromosomc to stay more often inside the egg, 

 and so increased the proportion of males, whereas 

 a lowering of the temperature had the contrary 

 effect. In the case of the frog, even if- the delay 

 does act in the way surmised, various difficulties 

 remain to be elucidated, and before definite con- 

 clusions can be reached as to sex-determination 

 in Amphibia, and fishes also, we require strict 

 genetical proof as to which sex in those animals 

 is heterozygous in the sex-factor. 



Much more serious difficulty arises from a class 

 of fact to which Standfuss was, I believe, the first 

 to introduce us. He found that in Lepidoptera 

 hvbridisation might affect the sexes differentially, 

 producing in certain cros.ses males only, in others 

 predominantly males (the few females being 

 sterile), and similar phenomena proving that the 

 influence of the cross was not alike for the two 

 sexes. A result obtained by an amateur named 

 Brake led Prof. Goldschmidt to investigate a most 

 remarkable case of such differential influence. 

 Lymantria dispar, the gipsy moth, is represented 

 by various races all over the northern temperate 

 regions. The sexes are very different, the male 

 being small and dark, the female large and pale 

 in colour. The original observation was that, 

 whereas crosses in the form Japanese 9 x Euro- 

 pean 6 gave in Fj the two sexes distributed as 

 usual, the reciprocal cro.ss, Hiuropcan 9 x Japan- 

 ese r^ , produced normal males, but females more 

 or less modified in the male direction. Kggs, 

 therefore, which, if fertilised by the sperm of 

 European males, would have produced females 

 gave rise to "intersexual females," as Prof. Gold- 

 .schmidt calls them, when the sperm came from 

 these Japanese males. To investigate this curi- 

 ous problem, he proceeded to Japan before the 

 outbreak of the war, and when Japan iK'came 

 involved he went to the United States, where he 

 was interned and encountered other serious difli- 

 culties when that nation also joined the Allies. 

 But in the course of his travels he was able to 

 collect and experiment with a long series of 

 species or local races inhabiting various parts of 

 Europe, Japan, nnfl Vorth Amcrirn, raising some- 



