26 J. PERCY BAUMBERGER 



11. Fruit is mainly the nutrient substratum for yeast cells, 

 but has some food value for larvae. 



12. By-products of fermentation are not necessary for larvae. 



13. Dead j^east is an adequate food for larvae when in a con- 

 centration of 2 per cent or more. 



14. Yeast is a more complete food for larvae than other 

 fungi. 



15. Concentration of banana by hot-water extraction or drying 

 makes it an adequate food for larval. 



16. The protein deficiency of fruit is quantitative rather than 

 qualitative. 



17. Agaricus campestris meets more nearly the food require- 

 ments of larvae than banana. 



18. Yeast nucleoprotein, sugars, and salts are an adequate 

 food for larvae. 



19. Yeast is a more adequate food than fruit because of its 

 higher protein content. 



C. Discussion, a. Effect of food on larval, pupal and adult 

 Hfe. On page 15 and in table 5 and figure 4 it has already been 

 shown that the concentration of yeast affects the length of the 

 larval period. This effect can be seen more clearly if we plot 

 the larval period on the axis of ordinates (vertical), of a graph, 

 and the number of grams of yeast per 100 cc. of water, in the 

 media, on the axis of abscissae (horizontal). A curve drawn 

 through the points established represents the effect of the concen- 

 tration of yeast upon larval life. This curve is drawn in figure 

 8. It changes its direction very suddenly at a point between 2 

 and 3 per cent of yeast, going up from a lar\^al life of 6.55 days 

 on 3 per cent tcJ a period of 11.40 days on 2 per cent yeast. If 

 we continue the curv^e in the same direction we approximate a 

 period of twenty days representing the larval life (which ends 

 in death) on 1 per cent yeast medium. This great change in the 

 direction of the curve indicates that there is a definite concen- 

 tration (2 per cent) of yeast necessary for the completion of the 

 larval period. Between yeast concentrations 2 per cent and 3 

 per cent there is a difference in the larval period of 4.95 days, 

 whereas between concentrations 3 per cent and 12 per cent there 



