32 



Dr. S. M. Copeman and Mr. F. G. Parsons. [Dec. i, 



" Observations on the Sex of Mice. — Preliminary Paper." By 

 S. Monckton Copeman, M.A., M.D., F.E.S., and F. G. Paksons, 

 F.R.C.S. Eeceived December 1, 1903, — Eead January 28, 

 1904. 



In this communication we record the results obtained, during a 

 period of fifteen months, from the breeding of fancy mice. The experi- 

 ments were commenced with the object of determining the extent, if 

 any, to which the relative proportion of the sexes is capable of being- 

 influenced by varying conditions of age, nutrition, inter-breeding, etc. 

 The work is still in progress, but in the hope of obtaining help and 

 criticism from other observers, we think it desirable to put on record 

 the experimental work that has already been carried out. 



Our paper consists of two parts : (a) a list of the various crossings 

 and their results, a record which we believe to be perfectly trust- 

 worthy j and (b) a series of conclusions at which we have arrived after 

 careful study of the figures. As these conclusions form the most 

 generally interesting portion of the paper, we have decided to place 

 them first, especially as the mere statistics are only likely to be of use 

 in the criticism of our deductions or in furnishing material by the aid 

 of which others, not at first apparent, may perhaps be formulated. 



In using these tables an explanation of our symbols may be 

 necessary ; it should, for instance, be noticed that all the bucks are 

 indicated by small Greek letters — the does by Roman capitals. When 

 a numeral follows the letter representing a particular doe, it shows 

 that the bearer is the daughter of the doe whose indication is the 

 letter alone. Thus, B 2 represents the second daughter which we kept 

 of B, while B 2,3 refers to the third daughter kept of B 2 , and, conse- 

 quently, the granddaughter of B. This method, of course, gives no 

 clue to the male ancestry of a mouse, but this can always be ascer- 

 tained by referring to the record of the particular animal. If we 

 translate one line taken at random from the doe's record it will, 

 perhaps, make our system clear : 



C 1 (to e). Sept. 22/02. 2 4 ? ( ? m., J at least 4 m.) 



This means that on September 22, 1902, C 1 (a daughter of C) bore 

 two males and four females to the buck e, and that at the time of 

 conception (some 20 days before) the mother was 3 J months old, 

 while the father was at least 4 months. On looking at the top of the 

 paragraph devoted to C 1 in the doe's record, her percentage will be 

 seen, while all that is known of the ancestry of e will be found at the 

 top of the paragraph devoted to him in the buck's record. 



