September 23, 1920] 



NATURE 



13: 



indicate the presence of one bristle factor in the sex 

 chromosome and another in the thirdi group, but the 

 exact relation of these to the increase in number of 

 Dristles has not been determined. The environment 

 also influences the number of bristles which appear. 

 In MacDowell's experiments forty-nine generations 

 were bred, and it was found that in a uniform environ- 

 ment selection had no effect after the thirteenth 

 generation ; statistical methods show that selection 

 failed to shift the modal condition, and no mutations 

 occurred during the experiments. 



In a study of the ettects of alcohol on white rats, 

 the same author (Proc. Nat. Acad. Sci., vol. iii., 

 p. 577) finds that alcoholised rats showed a consider- 

 able falling off in the weight of their offspring, and a 

 still greater loss in fecundity. Twenty-nine pairs of 

 normal rats produced three hundred young in the 

 same time that thirty alcoholised pairs produced one 

 hundred and eight young. He also (Proc. Soc. Exptl. 

 Biol, and Med., vol.' xvi., p. 125) finds that the children 

 and grandchildren of parents which had been treated 

 with alcohol for two months before the birth of their 

 young were less apt than the controls in learning to 

 run a maze or to make a multiple choice. 



The I^egumin'osae are well known to have usually 

 compound leaves, but several genera have unifoliolate 

 varieties, or even species. Blakeslee (Journal of 

 Heredity, April, 1919) describes such a form arising 

 as a mutation in the .Adzuki bean (Phaseolus angu- 

 laris). His studies of Datura (Blakeslee and .\very. 

 Journal of Heredity, March, 1919) have disclosed a 

 number of new forms differing from the type in shape 

 of capsule, foliage, and other characters. They 

 transmit their characters as a complex, chiefly through 

 the female, and in one instance a distinct new species 

 seems to have arisen which breeds true, but appears 

 to be sterile in crosses with the parent species. 



R. R. G. 



Increase of Population— a Warning, 



PROF. E. M. E.AST has much that is important in 

 his address as retiring president of the .American 

 Society of Naturalists, meeting at Princeton (Scientific 

 Monthly, vol. x., 1920, pp. 603-24). At present 

 there are about 1700 million people, with an annual 

 increase of between 14 and 16 millions. The white 

 race is increasing much more rapidly than the yellow 

 or the black. China's 300 million pojjulation is 

 practically stationary. With the exception of France, 

 few white peoples are increasing at a less rate than 

 10 per thousjmd. It is true that in most of the civil- 

 ised countries of the world the birth-rate is slowly 

 but stea<lily decreasing, but the result is not what 

 many would have us believe. Where the birth-rate is 

 ' low,' the death-rate is low, except in France. Prof. 

 East pre<licts that, owing to the steadily increasing 

 development of preventive medicine, the decrease in 

 the birth-rate will have no great effe<'t on the natural 

 increase In th<' world for many years to come. If the 

 fate of increase actually existent during the nineteenth 

 nturv in the Unitecl States should continue, within 

 span of life of the grandchildren of persons now 

 ng the States will contain more than a billion 

 ibitanls. " I.ong before this eventuality the 

 ggle for existence in those portions of the world 

 present more densely populated will b<> something 

 end the imagination of those of us who have lived 

 a time of plenty." The law of diminishing returns 

 even now in oooration in a comparatlvrlv new 

 ntry like .America, thought to be supplied with 

 xhauRtible riches. Prof. East considers in detail 

 that may be done by improved utili'^'>'"i" nf /.n<ri'ii-.. 



improved agriculture, improved breeding, and so on ; 

 but he is not sanguine. To the criticism that he has 

 not allowed for the " immense possibilities in the way 

 of utilising sea food," he responds with vigour. The 

 cloud grows denser when it is noticed that the birth- 

 rate of the foreign population of the United States, 

 coming largely now from eastern and southern Europe, 

 is so much greater than that of the .Anglo-Saxon stock 

 (to which, it is claimed, most of the superior types 

 belong) that within a century the latter will be but a 

 fraction of the whole. Prof. East looks forward to 

 severe restriction of immigration ; the spread of educa- 

 tion ; equitable readjustment in many economic cus- 

 toms ; rational marriage selection which will tend 

 to an increase of the birth-rate in families of high 

 civic value; and among the rank and file a restriction 

 of births commensurate with the family resources and 

 the mother's strength. 



Glass Technology. 



WE have received from the Department of Glass 

 Technology, University of Sheffield, a copy of 

 vol. ii. of "Experimental Researches and Reports" 

 published by that department. The papers included 

 have already appeared in the Journal of the Society 

 of Glass Technology. They range over a somewhat 

 wide field of the glass industry, and include papers 

 dealing with bottle-glass and glass-bottle manufacture, 

 chemical glassware, glass for lamp-working purposes, 

 besides accounts of such relevant investigations as the 

 accurate calibration of burette tubes, a simple ap- 

 paratus for the detection of strain in glass, and the 

 annealing temperatures of lime-soda and magnesia- 

 soda glasses. There are also a paper descriptive of 

 the glass industry of North .America and an account 

 of the year's progress in glass research under the 

 auspices of the Glass Research Delegacy. The 

 condition of the glass industry in this country un- 

 doubtedly calls for sustained and systematic research, 

 and this contribution of the Department of Glass 

 Technology of the University of Sheffield must be 

 of considerable assistance to what should be a great 

 and national industry. The newly founded Glass 

 Research .Association has also an extensive pro- 

 gramme of research in the field of what may 

 l>e called industrial and laboratory glass, and the 

 British Scientific Instrument Research Association is 

 also more particularlv concerned with investigations 

 into optical glass. With such a measure of co-opera- 

 tion and co-ordination as the development of the re- 

 searches shows to be necessar\' between these various 

 bodies, there Is hope that the users of all tvpes of glass 

 in this country may be able to find a home supply 

 equal, if not superior, to the foreipn sources to which, 

 before the war, they perforce had to go for much of 

 the glass they needed. 



NO. 2656, VOL. 106] 



Rate of Evolution. 



PROF. E. G. CONKLIN discusses {Scientific 

 Monthly, 1920, vol. x., pp. 58o-<>o2) the 

 difficult qiiestion of the rate of evolution, in- 

 cluding under evolution (a) diversification of 

 species, (b) more perfect adaptation to the condi- 

 tions of life, and (c) increasing differentiation and 

 integration, or, more briefly, progress. If the rate of 

 diversification ("divergent evolution") dep<-nds upon 

 the number of mutations that appear. Prof. Conklin 

 argues that it should be proportional, other thincs 

 Iic!n(< equal, to the rate of rrnrmluc tlon. But this 



