June i6, 1921] 



NATURE 



509 



Societies and Academies. 

 London. 



Royal Society, June 9.— Prof. C. S. Sherrington, 

 president, in the chair.— Prof. C. S. Sherrington : 

 Break-shock reflexes and "supra-maximal" contrac- 

 tion-response of mammalian nerve-muscle to single- 

 shock stimuli. The maximal twitch-contraction of 

 tibialis anticus muscle (cat) evoked by a single break- 

 shock applied to the cut motor nerve exceeds the con- 

 traction evoked reflexly (spinal preparation) by a single 

 break-shock applied to an afferent nerve. This is due 

 to the reflex response being tetanic in nature. If the 

 break-shock is strong it excites, even when applied 

 to the motor nerve, a response of tetanic quality. The 

 so-called "over-maximal twitch," now termed "'supra- 

 maximal response," is a response of this kind. A 

 reaction of like kind probably obtains in the aff^erent 

 nerve when the single-shock applied to it is of com- 

 parably high value. In this case there is also a 

 tetanic reaction from afferent nerve-fibres themselves. 

 With weaker break-shock stimuli the origin of the 

 tetanic character of the reflex discharge lies in the 

 centre itself. It arises there from a "charge " process 

 which is relatively long-lasting in comparison wnth 

 the cycle of a nerve-impulse, and increases in intensity 

 and duration with the number of afl'erent fibres 

 excited.— R. J. Ludford and J. B. Gatenby : Dictyo- 

 kinesis in germs-cells, or the distribution of the Golgi 

 apparatus during cell-division. Maturation mitoses 

 in the germ-cells of Cavia, Mus, Helix, Limnaea, and 

 Stenobothrus were examined. In all cases the Golgi 

 apparatus breaks up into its constituent granules, and 

 these are distributed haphazardly to the two, daughter- 

 cells at mitosis. In no case examined are they divided 

 between the daughter-cells as equally as are the 

 chromosomes. Hence the Golgi apparatus takes no 

 important part in the transmission of factors from 

 cell to cell.— Dr. F. W. Edridge-Green : The effect of 

 red fatigue on the white equation. A white equation 

 is formed by means of a mixture of a red of A6670- 

 6770 A., a green of A5 144-5 156 •^•' ^"^ ^ violet of 

 A4250-4267 A., matching a simple white. When the 

 eye is fatigued with light viewed through a red glass, 

 or with pure spectral light in the region of A6700 A., 

 and the equation is again made, about half the 

 amount of green is required. The white equation and 

 its match cannot be due to similar physiological pro- 

 cesses, or both would change in the same ratio. 

 When the fatiguing light is in the region of A7800 A., 

 no difference is seen between the mixed and simple 

 white. — E. Ponder : A method for investigating the 

 haemolytic activity of chemical substances. The 

 relation betw^een the time taken by a given quantity 

 of haemolytic substance and the temperature at w^hich 

 1 it acts is expressed by a hvperbola. The relation 

 between the constants of such a hyperbola and the 

 quantit}- of haemolytic substance to which it applies 

 are given. Certain general relations holrf for all sub- 

 stances examined. Experimental and calculated 

 results are compared. — W. H. Pearsall : The develop- 

 ment of vegetation in the English lakes, considered in 

 relation to the general evolution of glacial lakes and 

 rock basins. The English lakes are of the same age 

 (glacial), of similar origin, and lie among rocks pos- 

 sessing relativeh'^ uniform characters. The differ- 

 ences they show are due to variations in the rates 

 of erosion and sedimentation of the lake basins ; there- 

 fore it becomes possible to describe the stages in the 

 post-glacial development of a rock basin, and also of 

 its vegetation. The differences observed between 

 ^ primitive and evolved lakes are regarded as being 

 I dependent upon their physical condition. 



- NO. 2694, VOL. 107] 



Association of Economic Biologists, June 4.— Sir David 

 Prain, president, in the chair. — F. L. Engledow : The 

 problem of increasing the yield of cereal crops by plant 

 breeding. Aspects of experimental investigation, such 

 as breeding for disease resistance, non-lodging, or high 

 intrinsic yield, were considered, and the great diffi- 

 culty of obtaining any simple criterion for so com- 

 plex and elusive a total resultant as "yield" was 

 emphasised. Sevan's studies on the migration coeffi- 

 cient as an index of yield were destructively criticised. 

 The relation of yield to the weights of individual 

 grains, to the number of grains per ear, to the number 

 of ears per plant, and to the tillering of the plant was 

 considered. At present comparative estimates are 

 based on "yield per acre," but the author's work 

 suggests that "yield per tiller " may, perhaps, be a 

 better measure, "yield " itself being estimated in 

 terms of starch, carbon, or some other chemical 

 criterion, in place of the commercial standards now 

 accepted. — C. B. Sau-iders : Problems of seed testing. 

 The technique adopted at the official seed-testing 

 station for the testing of purity and germinative 

 capacity was described. Many problems arise in this 

 work of both a mechanical and biological nature. 

 Simple and effective instruments for sampling and 

 non-selective counting are required, as well as selec- 

 tive mechanical devices for the extraction of dodder 

 and other seeds from a mixture. Biological problems 

 largely concern the relation of seed germination to 

 environmental factors, and the apparent inconstancy 

 shown in this relation. Thus seeds of apparently the 

 same kind may under standardised conditions differ 

 considerably not only from year to year and from 

 month to month, but also from sample to sample, 

 and may show periodicities and external factor rela- 

 tionships which give rise to a very great cornplexity 

 of varying combinations. The whole technique is 

 empirical, and much fundamental research is needed. 



Cambridge. 

 Philosophical Society, May 16. — Prof. A. C. Seward, 

 president, in the chair.— Dr. E. H. Hankin : The 

 soaring flight of dragon-flies. From observation it 

 appears improbable that undiscovered wing-movements 

 or ascending currents of air can be accepted in ex- 

 planation of soaring flight. Alterations in the amount 

 of sunlight, even when slight, make considerable 

 differences in the flight of dragon-flies. Lowering of 

 the abdomen as a brake on speed in catching prey, 

 etc., is a common phenomenon. Dragon-flies, flying- 

 fishes, and birds ah exhibit soaring flight, and in each 

 class evidence is accumulating that low-speed flight 

 depends on the presence of sunshine and high-speed 

 flight on the presence of wind. If not identical, the 

 speeds attained in the three classes are comparable.— 

 C. G. Lamb : Note on secondary sexual characters in 

 the DIptera, with a description of a novel type. The 

 author discussed some points in the structure of the 

 hypopygium in flies, and gave a description of some 

 secondary characters in a new genus of Dolichopodidae 

 which were situated centrally instead of peripherally. 



L. A. Borradaile : A note on the mouth-parts of 



certain Decapod crustaceans. Some Decapods, as 

 Hapalocarcinus and Porcellana, seize food-particles 

 directlv ; others, as Pinnotheres and the Pontoniinae. 

 take it from sessile organisms. The mouth-parts of 

 the former are modified for their mode of feeding. 

 Similar modifications are not found in the latter, 

 possibly because their food reaches them entangled in 

 strings of mucus. Porcellana has no such jaw- 

 reduction as is found in Hanalocnrcinus, and this is 

 as vet unexplained. — J. Gray : Hermaphrodite sea- 

 urchins. — A. B. Appleton : (i) Preliminary note on the 

 development of muscle, bone, and body-weight in 



