SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICKOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



«« Embryology, f 



Nutrition and Sex Determination in Man. J— R. C. Punnett finds 

 that if the population of London be divided into three portions exhibit- 

 ing graduated poverty, the proportion of male to female infants is 

 lowest in the poorest portion, highest in the wealthiest portion, inter- 

 mediate in the intermediate portion. The proportion of male infants 

 is highest of all in a number of births taken from Burke's Peerage. 



Alternative conclusions may be drawn : that more favourable con- 

 ditions of nutrition (1) result in a large proportion of male births, or 

 (2) have no effect on the proportion of the sexes, or (3) may even 

 result in a relative preponderance of female births ; but that in the 

 last two cases the effect is masked by other factors which affect different 

 strata unequally. Such factors are shown to exist in a differential 

 infant mortality, a differential birth-rate, and probably also in a dif- 

 ferential marriage-age. These factors all tend to diminish the propor- 

 tion of males in the poorer portions of the population, and thus render 

 the first of the alternative conclusions improbable. Whether the second 

 or third is to be accepted cannot be decided until we are in a position 

 to estimate the quantitative effect of the factors noted above. Punnett's 

 opinion is that their combined effect would not be sufficiently great to 

 mask a preponderance of female births due to better nutrition, and 

 consequently he is inclined to believe that in man at any rate the deter- 

 mination of sex is independent of parental nutrition. In any case its 

 influence can be but small. 



* The Society are not intended to be denoted by the editorial " we," and tliey 

 do not hold themselves responsible for the views of the authors of the papers noted, 

 nor for any claim to novelty or otherwise made by them. The object of this part of 

 the Journal is to present a summary of the papers as actually published, and to 

 describe and illustrate Instruments, Apparatus, etc., which are either new or havo 

 not been previously described in this country. 



t This section includes not only papers relating to Embryology properly so called, 

 but also those dealing with Evolution, Development, Reproduction, and allied subjects. 



X Proc. Cambridge Phil. Soc, xii. (1904) pp. 262-76. 



