FOOD AS A FACTOR IN THE DETERMINATION OF SEX. 49 



to Gautier, contains from 8.43 per cent, to 10.72 per cent, of 

 lecithin. No attempt was made to feed tadpoles on lecithin alone, 

 because in experiments which I made several years ago the 

 mortality among tadpoles that were given lecithin as food was 

 exceedingly great ; the individuals dying evidently of starvation, 

 as they were never seen to eat any of the lecithin. Owing to 

 an accident, 100 tadpoles fed on the yolk of egg were killed the 

 second week of the experiment. Lot D, therefore, consisted 

 of only 200 individuals, making a total of 1,100 individuals that 

 are to be taken into account in considering the results of the ex- 

 periments in Series I. 



In order to make possible a comparison between the results 

 obtained in Series I. and those from similar experiments on the 

 eggs of a different female, a second series of experiments were 

 made beginning three days later than those in Series I. These 

 experiments were similar in all respects to those in the first series, 

 except that no attempt was made to investigate the possible influ- 

 ence of a scarcity of food in determing sex, and only 200 tadpoles 

 were used in each lot. Series II. therefore consisted of 800 

 individuals. 



Although detailed observations were made on each lot of tad- 

 poles at intervals of about one week, only the record of Series I. 

 for June 7, will be given. This record will serve to show the 

 differences between the individuals of the various lots that can 

 probably be ascribed to the varied character of the food that the 

 tadpoles received. 



Lot A. — The tadpoles fed exclusively on meat were noticeably 

 larger than those fed on any other kind of food. The largest 

 individuals measured 27 mm. in length, thus exceeding, by 3-4 

 mm., the length of a number of tadpoles of about the same 

 age that had been reared under natural conditions ; the smallest 

 individuals in this lot were 19 mm. long and were much larger 

 than many of the tadpoles in the other lots. Many of the 

 meat fed tadpoles had very well developed hind legs at this 

 time, but the front legs had not appeared in any individual as 

 yet. It was noticed that these tadpoles were very much blacker 

 than any of the other tadpoles being experimented upon. A 

 meat diet is evidently as favorable to the development of pigment 



