EFFECTS OF CHANGE OF FOOD. 335 



twenty-four hours at a temperature of 7° to 10° 0. (42° to 

 50° v.), twice at 10° to 15° C. (50° to 60° F.). thrice at 15° 

 to 20° C. (C0° to 69° F.), four times at 20° to 24° C. (69° 

 to 76° F.), and five times at 24° to 27° 0. (76° to 80° F.). 



At a temjierature of from 25° to 26° C. (76° to 78° F.) a 

 single Stylonicliia would in 7^ days have a progeny of 

 100,000,000,000, estimated 'to weigh 100 Ivilogrammes 

 (about 230 lbs.). With a vegetable diet the rate is much 

 less and the size smaller (C. R. Acad. Franc. 1887, pp. 1006- 

 1008). Maupas also shows that Infusoria continue to 

 multiply until the supply of food fails ; hunger then leads 

 them to conjugate. 



Vinegar eels (Vibrio) reproduce either viviparously or 

 by eggs, according to the nutritive medium and the tem- 

 perature. 



As is well known, the queen bee owes its greater size and 

 reproductive powers to being fed when a larva with royal 

 jelly. The same egg may yieid a worker or a queen, the 

 result being dependent on the richness of the food. 



While dimorphism is due to changes of temperature, the 

 extraordinary degree of polymorphism of the white ant, 

 one species being represented by eight kinds of individuals, 

 is apparently due to the nature of tlie food, as the males, 

 females, workers, and soldiers are at hatching all alike 

 (Grassi). 



In the vine-pest {Phylloxera vnstatrb:) the stoppage of 

 nutrition causes jjarthenogenesis to cease. 



It appears tliat the occurrence of a greater number of 

 females is the result of better food. Yung experimented 

 on tadpoles and reared more females when they were better 

 fed. In the first brood by feeding one set with beef the 

 percentage of females rose from 54 to 78; in the second set, 

 fed with fish, it rose from 61 to 81 ; while in the third lot, 

 when the especially nutritious flesh of frogs was supplied, 

 the percentage rose from 56 to 92, i.e., in the last case the 

 result of high feeding was that there were 92 females to 8 

 males. 



