April 19, 1906] 



NA TURE 



597 



SOCIETIES AND ACADEMIES. 



I ON1JON. 



Royal Society, December 7, 1905. — "On the Inheritance 

 of Coat Colour in Horses." By C. C. Hurst. Communi- 

 cated by W. Bateson, F.R.S. 



Analysis of the Stud Book shows that in thoroughbred 

 horses chestnut is a Mendelian recessive to bav and brown, 

 which are dominants. Omitting other colours, it appears 

 that when mated with chestnuts, bays and browns are 

 either (a) pure DD, giving no chestnut foal-, or (6) DR. 

 giving, on an average, equality of chestnuts and of 

 dominants. 



Chestnuts mated with chestnuts (of any ancestry) breed 

 (rue to chestnut, with about 1 per cent, of exceptions 

 (9 in 1 104), which may perhaps be due to errors in the 

 records. 



These observations differ from those of Prof. Pearson, 

 who found no intrinsic difference between the inheritance 

 of chestnut and other colours (Phil. Trans.. A. vol. cxcv.), 

 and has declared [Biometrika, ii., p. 2141 that Mendelian 

 principles do not applv to horse-colours. 



(Note added January 31.) 



In the paper read January 18 Prof. W'eldon disputes 

 these conclusions, while admitting that chestnuts breed 

 true with about 15 per cent, of exceptions. His argu- 

 ment depends on the recorded exceptions. The Stud Book 

 is very accurate, but many of the records are afterwards 

 corrected, and there is sufficient margin of demonstrable 

 error t" make it possible that the rare exceptions which 

 cannot be eliminated may be due rather to mistake than 

 to physiological peculiarity in the animals. Verv few of 

 the supposed exceptions have appeared in public uncorrected. 

 Genuine exceptions may perhaps occur, but the returns 

 have scarcely the extreme precision necessary to establish 

 such occurrences. Similarly the records show occasional 

 exception- to the purity of the pure dominants — about 

 1 per cent. 



It is no doubt by including the families in which these 

 exceptions occur among those from the DR dominants that 

 Prof. Weldon has found a large excess of dominants from 

 til. mating DRxR. 



Finally, the distinct properties of chestnuts must be 

 ascribed to segregation and not to ancestrv, for their 

 behaviour in heredity is entirely different from that of 

 bays and browns, though their ancestral composition may 

 for several generations have been the same. 



January 25. — " Observations and Photographs of Black 

 and Grey Soap Films." By Herbert Stansfield. Com- 

 municated by Prof. Schuster, F.R.S. 



This paper describes some work on soap film- that 

 originated with an examination of the two kinds of black 

 films, undertaken in connection with a continuation of 

 Reinold and Riicker's researches on soap films. The two 

 kinds of black soap film were first described bv Newton. 

 Reinold and Rucker made electrical measurements which 

 indicated that one black film was twice the thickness of 

 the other, and this result has been confirmed by Johonnott's 

 measurements with a Michelson interferometer. Johonnott 

 found that the limiting thickness of the thicker black was 

 12 nfi (micromillimetres), after which it changed abruptlv 

 to the thinner black, 6 /i/i thick. 



Vertical plane films were examined bv reflected light 

 with a low power magnification, and it was found that the 

 abrupt change from the thicker to the thinner black could 

 readily be observed with films made from a solution of 

 sodium oleate in water. It was also found that the change 

 from one black to the other was the last and most striking 

 of a series of similar changes that take place as a film 

 thins. The process of thinning appears to be continuous 

 and gradual until a thickness of about 100 n/* is reached, 

 but after that it is accompanied by a series of abrupt steps. 

 The photographs, taken with a camera and film box made 

 for the purpose, show the two black films and three 

 stages 1. .tween the coloured part of the film and the thicker 

 black which are called the first, second, and third greys, 

 the numbers increasing with the thickness as in Newton's 

 orders of colours. 



The photograph reproduced in Fig. 1 shows a vertical 

 frame, made of thin glass rod, supporting a film which is 



NO. 1903, VOL. 73I 



in the act of changing from the thicker to the thinner 

 black ; the small white discs that are formed on the 

 advancing boundary of the thinner black appear to consist 

 11I material removed in the process. A narrow line of the 

 first grey and traces of the thicker greys can still be seen 

 between the coloured part of the film and the black. 



A film shut up in an air-tight glass cell containing some 

 of the soap solution does not thin beyond the thicker black 

 stage if the equilibrium between the film and the water 

 vapour is not disturbed. The thinner black i- formed if 



9. Photograph showing 

 nts of the grey stages. 



evaporation takes place from the film ; it may be produced 

 by bringing a light near to the cell. Johonnott has recently 

 shown that the same effect can be produced by a sudden 

 increase of pressure in the cell. The change back again 

 from the thinner to the thicker bleck, or to still thicker 

 stages, can be produced by causing water vapour to con- 

 dense on the film. 



the paper also deals with the formation of the coloured 

 p. ii. In- which an- often seen moving down through a 

 coloured film. They have round heads and drawn out 

 tail-, and bear some resemblance to tadpoles. The head 

 often -how- concentric rings of colour, indicating that it 

 is like a convex lens in shape. These tadpoles, or lens- 



of theriln 



Showing a growth of solid n 

 ckenings falling through the 



oloured pari 



shaped bodies, often have their origin in minute grains 

 which form in the black at the top of the film. 



Fig. 2 -hows the way in which solid material sometimes 

 grows in a film. The film represented, instead of thinning 

 in the usual way ami becoming all black, only developed 

 a few millimetres of black at the top, and then continued 

 for hours to produce swarms of lens-shaped thickenings. 

 When a film is behaving in this way, the grains in the 



