320 SECTIONAL TRANSACTIONS.—D. 
5. Mr. W. Souruern. — The effect of wind upon the Distribution of 
Plankton. 
6. Dr. J. Davipson.—The Parthenogenetic and Sexual Phases im the 
Infe-cycle of Aphis rumicis, Linn. 
The conception of the earlier investigators regarding the appearance of the sexes 
in Aphides was that food and temperature were the influential factors concerned. 
Later investigations on the cytological aspect of the question indicate that internal 
factors associated with the chromosomes are the deciding factors. External factors 
may be considered as exerting an influence by retarding, restricting, or favouring the 
appearance of the sexes, but not as determining them. 
Aphis rwmicis has been bred in a pure line on Vicia faba continuously from 1920- 
1924, about eighty parthenogenetic generations having been passed through. While 
parthenogenetic reproduction was carried on throughout this period by viviparous 
females, sexual] forms appeared with marked regularity in September each year, and 
were produced in the colonies of succeeding generations until the following spring. 
Only parthenogenetic viviparous females were produced from May to September. 
The experiments afford considerable evidence that temperature is an important factor 
affecting the appearance of the sexes. It is clear that their appearance, being 
associated with a periodic rhythm, is an expression of climatic influences, which view 
is supported by the fact that several species of aphides are known to carry on partheno- 
genetic viviparous reproduction continuously in certain countries. 
In view of the results obtained from the breeding experiments, an investigation 
of the cytological aspect of the problem in Aphis rumicis should be carried out. 
7. Reports of Committees. 
AFTERNOON. 
8. Joint Discussion with Section I on The Functional Significance 
of Size. Opened by Mr. J. B. 8S. Hatpann. Other speakers : 
Dr. J. Wyman, Prof. D’Arcy THomeson, F.R.S., Dr. A. E. 
Boycort, F.R.S. 
Friday, August 28. 
Mornine. 
9. Presidential Address by Mr. C. Tate Regan, F.R.S., on Organic 
Evolution. (See page 75.) 
Followed by discussion. 
10. Dr. F. A. Dixy, F.R.S.—On the Development of the Androconia 
(scent organs) in the Small Garden White Butterfly (Ganoris rape). 
11. Miss Rura C. Bameer (Mrs. Bisper) and Miss HE. CaTHERINe 
HerpmMan.—A Contribution to the Study of the Inheritance of 
Black and Yellow Coat Colour in Cats. 
Records on the inheritance of coat colour in cats show that either black or yellow 
or both must be sex-linked, and that a male cat cannot normally show both black 
and yellow in his coat. As both these characters are recessive to all other common 
coat colours, their exact condition with regard to sex linkage has not yet been 
determined. 
In 1923 the mating yellow g x tortoiseshell (black and yellow) 9 produced a yellow 
? kitten with a small fleck of black on the right hind foot. This cat, when mated to 
