loo POPULAR SCIENCE MONTHLY. 



by Lowne that individuals from the large maggots that have been well 

 nourished are nearly always females, while those from small maggots, 

 poorly nourished, are usually males. Cuenot first determined, in the 

 three genera used in his experiments, that normally the number of 

 males and of females is about the same. The results of his experi- 

 ments, in which the maggots were well fed, were as follows — in Lucilia 

 ccesar 49.27 per cent, of females; in Calliphora vomitoria 51.02 per 

 cent, of females; and in Sarcophaga carnaria 51.62 per cent, of females. 

 It is obvious that the presence of an abundance of food did not produce 

 an excess of females. In another experiment in which the maggots 

 received as small a quantity of food as possible there was great mortality 

 and the pupae were of diminutive size. The results were as follows — 

 Lucilia ccesar 57.92 per cent, of females; Calliphora vomitoria 57.92 

 per cent, of females; and Curtonerva pabulorum 26 females and 17 

 males. It is even more evident from the results of this experiment 

 that starving does not have the effect of producing an increase in the 

 number of males. Several variations of these experiments were made, 

 but the results were always the same. Cuenot also tried to find out if 

 the amount of food taken by the individual during its growth has any 

 effect on the kinds of eggs that are produced. The larva? of Calliphora 

 vomitoria were starved from their birth until they pupated. They 

 gave rise to twelve males and five females, whose size was scarcely half 

 that of the normal individuals. These dwarf flies, confined in a cage 

 with sweetened water and meat, laid twenty times. The larvae that 

 hatched were kept in a well-nourished condition, and gave rise to 359 

 females and 353 males. The results show that the amount of food 

 supplied to the young maggots had no effect upon the relative number 

 of male and female eggs that they produced. It is true that these 

 animals, when poorly nourished, gave rise to only a few eggs, but the 

 relative number of eggs that became male or female remained the 

 same. 



Among the earliest experiments that were carried out to show 

 whether the sex of the individual could be determined by external condi- 

 tions were those of Born in 1881, and of Yung in 1883 and 1885. Born 

 tried to show that more male frogs develop when the fluid containing 

 the fertilizing spermatozoa is more concentrated, but this conclusion 

 has been shown to be wrong. Born also fed the tadpoles of Rana 

 iemporariu on a rich diet consisting of water plants and of the flesh of 

 frogs and of tadpoles. A large percentage of females developed which 

 Born attributed to the abundance of food. It was shown, however, by 

 Pfliiger in the following year, 1882, that Bom's conclusion was 

 erroneous, because, even under normal conditions, female frogs are 

 more numerous. Pfliiger found that the normal proportions of females 

 to males is often as high as five to one ; and this corresponds also to the 



