July 22, 1920] 



NATURE 



655 



further researches, and that it will be fruitful not 

 only in helping to a fuller understanding of the laws 

 of the colloidal state, but also in suggesting new 

 applications for colloids in the laboratory and in the 

 works. The exact date and place of meeting and 

 further particulars will be announced later. In the 

 meantime, anyone desirous of using the opportunity 

 of the discussion to bring forward experimental matter 

 or theoretical considerations bearing on the above- 

 mentioned branches of the subject is asked to com- 

 municate as soon as possible with the secretary of the 

 joint committee, Mr. F. S. Spiers, lo Essex Street, 

 London, W.C.2. 



A SPECIAL meeting of the Rontgen Society was held 

 on July 15 in the chemical theatre of University Col- 

 lege, London, by kind permission of the authorities. 

 The occasion was an address by Dr. W. D. Coolidge, 

 director of the research laboratories of the General 

 Electric Co., of Schenectady. An audience of more 

 than 250 people gathered to hear from the inventor 

 of the X-ray tube which bears his name a detailed 

 account of the processes involved in the manufacture 

 of the Coolidge tube — or rather we should say the 

 Coolidge tubes, for a number of different types of 

 tube, each suitable for different working conditions, 

 are the outcome of the investigations carried out under 

 Dr. Coolidge 's direction over a number of years. Dr. 

 Coolidge in his address laid considerable emphasis 

 upon the amount of investigation entailed in the use 

 of tungsten either as a hot filament or as the target 

 of an X-ray tube. The welding of this highly brittle 

 metal and its perfect annealing with copper are 

 technical triumphs, and the details of these processes 

 in their final stages were of very great interest. 

 While the effort is at present being made by the 

 General Electric Co. to standardise radiographic pro- 

 cedure by combining a high-tension outfit which auto- 

 matically limits the quantity and quality of the X-rays 

 from the tube, it is recognised that no such procedure 

 is possible in radio-therapy at the present day. The 

 limitations imposed upon the production of very 

 short wave-length X-rays are largely technical ones, 

 and we look with confidence to their production in the 

 near future, for both in medical work and in the 

 examination of metals and other materials they are 

 likely to prove of great value. If the production of 

 these more penetrating radiations involve new ideas 

 in the construction of the X-ray tubes, those who 

 heard Dr. Coolidge 's address will feel that such con- 

 siderations will not be allowed to delay what is 

 becoming a seriously felt want. 



In a paper read before the Royal Statistical Society 

 in April (Journal, 1920, vol. Ixxxiii., part 3, pp. 1-44), 

 Dr. T. H. C. Stevenson presented the results of an 

 inquiry into the fertility of the various social classes 

 in England and Wales from the middle of the nine- 

 teenth century to 191 1. Cfiild mortality varies 

 directly and very markedly with the number of 

 children born and the rapidity with which they 

 are born. It also varies with the age of the mother 

 at birth. If allowance is made for the differences 

 of marrying age in different classes, fertility is found 

 to increase downwards throughout the social scale. 

 NO. 2647, VOL. 105] 



The difference in fertility between the classes is, 

 broadly speaking, a new phenomenon, for it is small 

 for marriages before 1861, and rapidly increases to a 

 maximum for those of 1891-96. That the decline in 

 the birth-rate is due to the artificial restraint of fertility 

 is indicated by the following features : The gradual 

 spread of the decline throughout society, from above 

 downwards ; the exceptionally low fertility of occupied 

 mothers ; and the increase in the defect for the higher 

 social classes with increase of duration of marriage 

 up to twenty-five years. The lowest fertility rates are 

 returned for the most purely middle-class occupations 

 — the professions. The comparatively low child mor- 

 tality of the less fertile classes goes but a small way 

 numerically to compensate for their low fertility. 

 The classes which are least fertile when married are 

 likewise those that marry latest in life. Ante-nuptial 

 conception leads to great under-statement of the 

 number of marriages of less than twelve months' dura- 

 tion. Such under-statement is the rule amongst all 

 classes where the wife's marriage age is under twenty, 

 and becomes less frequent as the wife's age increases. 

 At ages above twenty its frequency varies with the 

 social position, reaching its maximum amongst un- 

 skilled labourers. 



Prof. E. W. MacBride contributes to the latest 

 number of Scientia (vol. xxviii.. No.. 99, 1920) a 

 trenchant article on "The Method of Evolution." By 

 the "force of heredity," he says, is meant the 

 tendency of the offspring to resemble the parent. It 

 is obvious that in some way this force must be 

 modified as time progresses, otherwise evolution could 

 not take place, and the manner and means of this 

 modification are just what we mean by the phrase 

 "method of evolution." The Darwinian view that 

 large results may be reached by the selection of small 

 individual variations is seriously weakened by "pure 

 line " experiments. The mutationist view of the im- 

 portance of " sport "-variations exhibiting Mendelian 

 inheritance cannot be accepted as more than an acces- 

 sory theory, for most mutations are of the nature of 

 "cripples," and utterly unlike the differentiating 

 characters which distinguish allied species. There 

 remains a third alternative : the inheritance of the 

 effects of use and disuse. This is the method of 

 evolution, " the dominating influence which has 

 moulded the animal world from simple beginnings 

 into the great fabric of varied life which we see 

 around us." If we ask for evidence of the trans- 

 mission of somatic modifications, we are referred by 

 Prof. MacBride to the researches of Kammerer. If 

 we submit that opinion is divided as to the validity of 

 these, we are told to repeat the exi>eriments, which 

 is, of course, a fair enough answer. In the mean- 

 time, we are invited to consider how bacteria, 

 modified to perform feats in disruptive chemistry 

 of which their ancestors were incapable, hand on 

 their individually acquired new qualities to their 

 abundant progeny. And if we suggest that this is not 

 a test case, since bacteria have no soma and do not 

 multiply by germ-cells, we are told that the distinc- 

 tion between somatoplasm and germplasm is a 

 "Weismannian nightmare.'" All this points clearly 

 to the need for fresh exoeriments. 



