LINNEAN SOCIETY OF LONDOK. 



renders them a serious menace to oyster-culture, as likewise the 

 necessity for individually chopping them off by " cultack " before 

 the oysters are presentable for sale. 



Prof. A. Dendy and tlie President made remarks, and Dr. Murie 

 briefly replied. 



Mr. Alfred O. Walker exhibited Clerodendron trichotomum, 

 Thunb., in fruit, a result of the past abnormal summer, explaining 

 that, although the plant frequently flowered in England, this year 

 is the first time it had fruited, the same occurrence being also 

 observed at Kew. 



Mr. R. S. Bagnall briefly i*eferred to three interesting captures 

 lie had lately made in the county of Durham, namely, species of 

 Di^ylopora and Pauropoda, and of Protunt first recorded as British. 



November 16th, 1911. 



Dr. D. H. Scott, M.A., F.R.S., President, in the Chair. 



The Minutes of the General Meeting of the 2nd November, 

 1911, were read and confirmed. 



Mr. James M'Crone Douie, C.S.I., Mr. John William Haigh 

 Johnson, B.Sc, and Miss Beatrice Lindsay, were proposed as 

 Pellows. 



Dr. Ebgixald R. Gates, M.A., Ph.D., then gave the main 

 outlines of his paper, communicated by Dr. Marie Stopes, F.L.S., 

 on " Certain aspects of the Mutation Problem in Oenothera." He 

 stated that : — 



Work with the Oenotheras has developed in several directions, 

 all bearing on the general question of the place to be assigned 

 to mutation as an evolutionary factor. An investigation of the 

 behaviour of the Oenotheras in heredity and variation from several 

 points of view, gives a broader basis for the interpretation of the 

 evolutionary significance of these phenomena than has hitherto 

 been possible in most other genera. 



The cj^tological evidence shows that in most of tlie mutants 

 from Oenothera LamnrcJciana the chromosome number is unchanged, 

 but in the mutant O.glgas it is doubled. Hence mutants originate 

 in various ways. Evidence tends to show that the chromosome 

 doubling in 0. gigas probably occurred either in the fertilized e^^g, 

 or in a megaspore mother-cell which afterwards developed apo- 

 gamously. 



On tlie other hand, in certain cases the mutational change 

 probably occurs during the reduction divisions. Thus 0. rubri- 

 cahjx is a mutant from 0. rubrinervis which produces an extreme 



62 



