452 Vererbung, Variation, Mutation. 



mating wliich increases the probability of like gametes uniting to form zygotes. 

 While the statement is correct, the general conclusion can more usefully be sta- 

 ted as follows: An increase in the proportion of homozygotes in the population 

 will follow Inbreeding of any sort, though at differeut rates for different types 

 of Inbreeding, because any Inbreeding involves homogamy (or assorta- 

 tive mating) in some degree. 



The remainder of the paper deals with the results which follow from con- 

 tinued brother-and-sister mating in a Mendelian population. 



It is shown that if we begin with a population composed eutirely of indi- 

 viduals heterozygous (Aa) for one character, calling this the first generation, and 

 if the matings be only brother and sister, then the Fg and the Fg will each con- 

 tain 507o of homozygotes, theF^ 62.5% homozygotes, the F5 68.75%, F^ 75*' q etc., 

 gradually approaching a completely homozygous condition of the population. 

 There is no fundamental difference between self-fertilization and all other fornis 

 of Inbreeding in respect to homozygosis. Gates. 



1197) Wheldale,M. and Bassett, H. L., The Chemical Interpretation of 

 Some Mendelian factors for flower-colour. In: Proc. Royal Society, 

 Bd. B 85, Nr. 595, S. 300—311, 1914. 



On the basis of the chemical investigation of the flower pigments pre- 

 viously published (Biochemical Journal VII, p. 441 etc., 1913), and of fresh in- 

 vestigations described in the present paper, the authors draw the foUowing con- 

 clusions. The yellow pigment of Anürrhinum is luteolin, and the factorial diffe- 

 rence between yellow and ivory consists in the ability of the yellow form to 

 produce luteolin in addition to, or probably instead of, apigenin. From the white 

 variety no flavones could be extracted. Anthocyanin pigments are probably 

 derived from flavones by oxidation or by condensation, but this is not yet proved. 

 In discussing the recently published work of Keeble, Armstrong and Jones 

 (Proc. Roy. Soc, Vol. B 87, p. 113, 1913) the authors decide that the con- 

 clusions drawn by these latter investigators are not necessarily justified by the 

 facts, and that two alternative explanations are possible. Doncaster. 



1198) Mac Bride, E. W., Studies in Heredity. IL Further Experiments 

 in Crossing British species of Sea-urchins. In : Proc. Royal Soc, Bd. B87, 

 Nr. 594, S. 240—245, 1914. 



In a previous paper (Proc. Roy. Soc. B 84, 1911) the author found that the 

 early larvae from the cross Echmocardium cordatum 5 X Ecliinus esculcnhis S 

 were intermediate in character, while Ecliinus eggs fertilized by Echinocardium 

 produced a membrane but failed to develop. Fuchs, from the cross EcJnnus $ 

 X EcJiinocardÜDu S got larvae which were purely maternal in character, while 

 the converse cross gave some maternal and some intermediate larvae (Arch. 

 Entwick.-Mech. 35, 1912). On repeating his experiments, Mac Bride got larvae 

 from one Eclnnus $ which were purely maternal, so agreeing with Fuchs. Most 

 of the eggs, however, broke up into globules and degenerated, as in the previous 

 experiment, and usually when blastulae were produced they were abnormal, with 

 enormous excess of mesenchyme cells. To test whether the granulär degenera- 

 tion usually found in the crossed eggs is a consequence of hybrid fertilization, 

 eggs from an Echinocardium $ were divided into two lots, one of which was 

 fertilized by Echinus sperm. The next day the fertilized eggs were all cytolysed 

 and dead; the unfertilized eggs still clear. Of the latter, one portion (a) was 

 fertilized with Echinocardium, another (b) with Echinus sperm, a third (c) left 



