TRANSACTIONS OF SECTION -D, GS5 



In concluding, I must ackno'svledge the assistance I have obtained by dis- 

 cussing the local scheme with tlie members of the executire committee of the 

 Cambridge Entomological and Natural History Society, Avhich intends commencing 

 a fauna of Cambridgeshire on the lines suggested. 



Some Notes on the Behaviour of young Gulls artificially and naturally 

 hatched, — See Reports, p. 378. 



4. Tlie Theory of ^ Germinal Selection' in Relation to the Facts 

 of Inheritance.^ By Professor J. Arthur Thomson, M.A. 



The aim of this communication was to test Weismann's theory of germinal 

 selection by using it as an interpretation of some important facts of inheritance. 

 The author gave a brief abstract of the theory. It is an extension in the applica- 

 bility of the general idea of natural selection. To ' superorganic ' selection, 

 ordinary 'individual' or 'personal' selection, Koux's 'histonal' or intra- 

 organismal selection, Weismann has added the idea of a struggle among the 

 determinants within the germ — germinal selection. 



The author indicated the importance of a form of struggle between Roux's 

 histonal selection and Weismann's germinal selection, namely, the struggle between 

 gametes or potential gametes, e.g., between young ova, between sperms, even 

 between ova and sperms. A vivid realisation of this visible struggle, and the 

 sometimes discriminate selection which it implies, may lead naturally to an 

 appreciation of germinal selection which deals with the wholly invisible. 



The following extension of Weismann's idea of gerininal selection was pro- 

 posed as logical and necessary : — Just as there are three types of individual 

 struggle, (1) between hindred organisms, (2) between organisms not akin, and 

 (3) between organisms and the so-called inanimate environment ; so there may be 

 (1) struggle between determinants of the same character, (2) struggle between 

 different kinds of determinants (AVeismanu), and (3) struggle between all or any 

 of the determinants and the somatic or more external environment. 



After stating the advantages of Weismann's theory and possible objections, 

 the author proceeded to test it in relation to various facts of inheritance : — 

 (1) The frequently anomalous and unpredictable nature of the results of a pairing 

 even when the pedigrees are well known ; (2 ) the phenomena of preponderant 

 and exclusive inheritance ; (3) some of the results of the ' Penycuik experiments ' 

 on the importance of the relative ripeness of the gametes; (4) some well- 

 established cases of true reversion ; (5) the supposed greater stability and domi- 

 nance of the phylogenetically older characters; (6) inbreeding; (7) different 

 modes of variation, including De Vries' mutation ; and (8) the indirect eti'ect which 

 exogenous changes may have on the germ plasm. 



The author's conclusion was that Weismann's theory of ' germinal selection ' 

 justifies itself provisionally as a formula unifying a large number of otherwise 

 unrelated facts of inheritance. 



5, The Heterotypical Division in tlie Maturation Phases of the Sexual 

 Cells. By Thomas H. Bryce, M.A., M.D. 



Of the features of Heterotypical Mitosis the one generally selected as distinc- 

 tive is the ring form of the chromosomes, each ring being considered to arise from 

 the incomplete separation of the two products of the longitudinal cleavage of a 

 primary chromatin rod. The manner in which these ring chromosomes are 

 resolved has been variously interpreted. For the purposes of this note it will 

 suffice that three interpretations be summarised, thus : — 



' The paper will be included in the author's work on Heredity (John Murrav, 

 1902). 



