27 



two forms found in Egypt, these forms being also more easily 

 distinguished by theii' colour chai'iicteristics. 



Mr. Bonhote in dealing with the Rats of this species from the 

 Oriental Region had some yeais ago subdivided them into tlu'ee 

 subgroups, and it was now shown that tlie size of the feet typical 

 of the three Oriental subgi-oups corresponded with the three 

 apices in the curve of the Egyptian forms. 



The author was inclined to think that these apices represented 

 centres of variation and were probably inherited as Mendelian 

 characters, for were this not the case the smallest apex would 

 have become swamped antl a regular cui-ve would I'esult. 



It was, however, evident that the small foot chai-acter was 

 present and ready to become the dominant form in a very short 

 time should conditions giving advantage to a small foot arise. 



On comparing the curve of the hind feet of Mus norreyicus, 

 three apices were also observed, showing that in this species the 

 " hind foot character " was also present, but as there wei-e no coi*- 

 responding colour differences it was impossible to tell to which 

 gTOup any particular individual belonged. 



The author drew the following conclusion, viz., that there was 

 considerable ^jri?«« facie evidence that the size of the hind foot 

 and the colour of the hairs on the imderparts were Mendelian 

 chai'acters, and pointed out that the former cliai'acter was also 

 found in another species, JIus norvegicits, and the latter in a third 

 species, Mits onuscidus. 



On the presumption that these were true Mendelian characters 

 a clearer understanding was at once gained as to how species 

 might very Cjuickly adajit themselves to altered conditions, and 

 how many very closely alHed species, differing onl}'^ in size or in 

 some definite but slight alteration of colour, could exist in the 

 same locality and yet maintain their characteristics intact and 

 show no merging of the one into the other. 



Experiments in breeding the different foi-ms wei-e being under- 

 taken, but they were not as yet sufficiently advanced to pcimit of 

 any definite results being stated. 



j\Ir. G. E. Bulled presented a pnper, connnunicated by Mr. 

 John HorKiNSOX, F.Z.S., " On an Example of Posterior Dichotomy 

 in an Aylesburj^ Duckling," giving a detailed account of a dissec- 

 tion performed on a duckling having supernumerary legs. In 

 addition to a reduplicated pelvis and the usual condition of the 

 limbs presented in posterior dichotomy, it was found that the 

 specimen showed evidence of a further reduplication of the part 

 dichotomised. 



