upon the determination of sex in rabbits. 93 



During the past year Russo's experiments have been repeated 

 by Basile* with negative results. From six injected does he had 

 117 young in 17 litters, and of these 66 were (/cf and 51 were 

 $ ? . He also bred 60 litters from nine rabbits which were not 

 injected, and of the 440 offspring 225 were (/*(/ while 215 were 

 $ $ . Among the offspring of the uninjected the proportion of 

 females was actually slightly higher than among the injected. 



Being desirous of repeating Busso's experiments I wrote to 

 him in February, 1908, asking for certain details in his method. 

 He very kindly sent me the information for which I had asked, 

 and at the same time informed me that he had produced similar 

 results by feeding with lecithin in place of the injection. My 

 experiments were carried out in accordance with the details of the 

 feeding method of which he sent me particulars. An emulsion 

 was prepared by shaking up 5 grams of lecithin (Merck) with 

 1000 c.c. of physiological salt solution ('65 %). The daily dose for 

 each rabbit was 20 c.c. of this emulsion made up into a paste 

 with meal, and the treatment was continued for three months 

 before the doe was put to the buck-f-. I also went on with it for 

 a few days subsequent to this. No difficulty was experienced in 

 getting the rabbits to take their daily dose, for they soon became 

 exceedingly fond of it and ate it greedily as soon as it was offered 

 them. During the past summer 10 does were treated in this way, 

 and they eventually produced between them 47 young. Of these 

 24 were ^f^ and 23 were $ $ . From these and other does not 

 treated with lecithin I have had 18 litters with 103 young, and of 

 these 54 were (/(/ and 49 were $ $ . In either series of experi- 

 ments the numbers are not large, but so far as they go they are 

 entirely opposed to the view that feeding on lecithin has any 

 influence on the relative proportion of the sexes among rabbits. 



* Atti Acad. Lincei, 1908, Vol. xvii. 1, p. 643. 



t Here I would express my thanks to my friend Mr F. A. Potts for kindly feeding 

 the rabbits for me during a week when I was absent from Cambridge. 



