August i6, 1900J 



NATURE 



The following table gives the mean length of life of parents 

 taken singly and of parents weighted with their offspring : — 



Now these are substantial differences even in the case of the 

 English parents, but they are very large differences in the case 

 of the American parents. If we suppose no assortative mating 

 on the basis of characters tending towards longevity, then it is 

 easy to measure by a rough approximation the effect of repro- 

 ductive selection in modifying the duration of life. 



The increased duration of life would be about two years per 

 generation from the American data, and about 9 to 9-5 months 

 per generation from the English data. 



The result for the American series shows us how an especially 

 low expectation of life, due possibly in this case to some family 

 character, will be rapidly raised by reproductive selection, if 

 there be no opposing factor of evolution. The English results 

 on the other hand show us a small, but sensible, tendency in re- 

 productive selection to prolong the duration of life. Allowing 

 three generations to a century, we might expect the duration of 

 life to be raised about two years in a century by this factor of 

 evolution. 



A somewhat widespread view of evolution stops at the survival 

 of the fitter without discussing the mode whereby the less fit 

 leave no, or fewer, offspring than the fit. Of course, if the un- 

 fit are exterminated before adult life, there is no chance of their 

 reproducing themselves. It has been shown in " Data for the 

 Problem of Evolution in Man (II.)" that a selective death-rate 

 exists for adults, so that the whole work of selection does not take 

 place before the reproductive stage is reached. But Miss Beeton's 

 data for the correlation of duration of life in the case of brethren 

 dying as minors seem to show that the selective death-rate for chil- 

 dren is rather less, not greater, than its value for adults. ' Hence, 

 for the reduction or extermination of stock unsuited to its en- 

 vironment, we should have to look largely to selection in the adult 

 state. In the present paper we have made what we believe to 

 be the first quantitative determination of how a selective mor- 

 tality reduces the numbers of the offspring of the less fit relatively 

 to the fitter. In the case of life under wild conditions, the cor- 

 relation between fertility and power of surviving would probably 

 be far greater. But for such life it is almost impossible to get 

 statistics of this nature ; we are thrown back upon measuring 

 the effect in man, and thus obtaining what may well be con- 

 sidered as a minimum value of the influence under discussion. 



In the course of our investigations we have found that the 

 relationship between fertility and duration of life does not cease 

 with the fecund period. We thus reach the important result 

 that characters which build up a constitution fittest to survive 

 are also characters which encourage its fertility. This result is 

 of great value from the standpoint of the differentiation of type, 

 where it is absolutely necessary that the fittest to survive should 

 also be the most fertile. On the other hand, we note that dura- 

 tion of life is a character capable of modification by reproductive 

 selection, and we suggest that a considerable part of the in- 

 creased expectation of life observed in recent years may be due 

 to this cause. In the case of the American statistics, we see at 

 once how reproductive selection can replace a remarkably short- 

 lived stock by a longer-lived stock, for the bulk of the offspring 

 come from the longer-lived members. 



Paris. 



Academy of Sciences, July 30.— M. Maurice Levy in 

 the chair. — On the observatory at Mount Etna, by M. J. 

 Janssen. Remarks on local difficulties due to climatic disturb- 

 ances and to the peculiar situation of the observatory. — New 



1 The point is still under investigation.- 

 NO. 1607, VOL. 62] 



processes of vaccination against symptomatic carbuncle of the ox 

 by means of preventive serum in association with vaccines, by 

 M, S. Arloing. A continuation of former experiments on the 

 subject. — On the age of the sea-shore sands of Dunkirk, by 

 M. J. Gosselet. The formation of these deposits is considered 

 to have commenced since the fourth or fifth centuries. — M. 

 Duhem was elected a corresponding member for the section of 

 mechanics. — Observations of Borrelly's comet (July 23, 1900) at 

 the Paris Observatory, by M. G. Bigourdan. — Provisional 

 elements and ephemerides of the Borrelly-Brooks' comet (July 

 23, 1900), calculated by M. G. Fayet. — On the spectral images 

 of the chromosphere and protuberances obtained with the prism- 

 atic chamber, by M. Georges Meslin. A description of the 

 results obtained with the apparatus previously described. — On 

 two surfaces related to every Weingarten's surface, by M. A. 

 Demoulin. — On artificial radio-active barium, by M. A. 

 Debierne. Many substances become radio-active when brought 

 into intimate contact, by solution or simultaneous precipitation, 

 with radio-active compounds. Artificial radio-active barium chlor- 

 ide, intermediate in character between barium and radium, has 

 thus been obtained. — On the thermo-electricity of steels, by M. G. 

 Belloc. A comparative study of the thermo-electric properties 

 of soft iron, soft steel, and hard steel.— On a means of weaken- 

 ing the influence of industrial electric currents on the terrestrial 

 field in magnetic observatories, by M. Th. Moureaux. An 

 account of the methods whereby the disturbances caused by 

 electric tramways in the neighbourhood of observatories may 

 be removed or corrected for. — On the electrolysis of concen- 

 trated solutions of hypochlorites, by M. Andre Brochet. The 

 electrolysis of hypochlorite resembles, in its later stages, that 

 of alkaline chloride solutions, and tends towards the same 

 limits. There is, therefore, little hope of obtaining concentrated 

 solutions of hypochlorites by the direct electrolysis of chlorides. 

 —On gadolinium, by M. Eug. Demar9ay. A study of the 

 spectrum of gadolinium — On diphenylcarbazide as a sensitive 

 reagent for some metallic compounds, by M. P. Cazeneuve. 

 The conversion of diphenylcarbazide into diphenylcarbazone by 

 the action of salts of copper and mercury and the persalts of 

 iron, as recently described, furnishes a delicate test for these 

 metals. The latter unite with the carbazone to form coloured 

 compounds. — Preliminary study of the chemi.sm of the en* 

 cephalon, by M. N. Alberto Barbieri. Experiments on the 

 chemical changes occurring in the brain of animals when 

 left for twelve to eighteen hours at a temperature of 45°, 

 — On the dissolution of the nitrogenous constituents of 

 malt, by MM. P. Petit and G. Labourasse. Experi- 

 ments relating to the existence of a proteolytic enzyme 

 in malt.— Action of the liquid from the external prostate of the 

 hedgehog on the liquid of the seminal vesicles ; nature of this 

 action, by MM. L. Camus and E. Gley. — On some properties 

 and reactions of the liquid from the internal prostate of the 

 hedgehog, by MM. L. Camus and E. Gley. This and the 

 previous paper form a continuation of the authors' researches on 

 the coagulation of the secretion of the seminal vesicles by that 

 of the external prostate, or Cooper's gland, and the coagulation 

 of the latter secretion by that of the internal prostate.— On some 

 Alpheidoe of the American coasts, by M. H. Coutiere. An 

 account of some specimens in the collection at the United 

 States National Museum, Washington. 



August 6.— M. Maurice Levy in the chair. — The menstrual 

 function and rut in animals. Function of arsenic in the economy, 

 by M. Armand Gautier. The author has found that the quan- 

 tities of arsenic and iodine, which in normal blood are hardly 

 estimable, are largely increased during menstruation, the total 

 amount of arsenic eliminated during one period of menstruation 

 representing the whole amount usually present in the thyroid 

 gland. The arsenic and iodine which accumulate in the thyroid 

 gland are eliminated in the male by the hair and nails, and by 

 epithelial desquamation. In the female, this excess is either 

 eliminated by the genital organs or utilised by the growing 

 fcetus. — Observations of the star Capella, considered as a 

 double star, made at the Greenwich Observatory, by Mr. 

 W. H. M. Christie. The independent discovery by Camp- 

 bell and Newall, by spectroscopic observations, that Capella 

 is a double star, has been confirmed by direct observation with 

 the large Greenwich equatorial. The star appears distinctly 

 elongated in one direction, the distance of the two components 

 being estimated at o"! second. Observations of the direction 

 of this elongation, taken between April 4 and July 20, confirm 



