ALIMENTARY CANAL TN THE BEE 539 



only in cases which do not require long conservation of the 

 material analysed, since the extracts rapidly decompose. 

 A very suitable solvent for invertase, as regards resistance, is 

 presented by a mixture of glycerine and water. Our experi- 

 ments have shown that extracts prepared in this mixture 

 retain their original activity at least during eleven months 

 (Table IX). Glycerine, on the other hand, suffers from another 

 defect : it acts depressively on the course of inversion, as is 

 clearly visible from the series of experiments nos. 35, 36, 37 

 of Tables VI and VII and Curves 2 and 3. As in the preceding 

 experiments invertase manifests its activity in different sol- 

 vents also only during the first days. 



In order to determine the durability of invertase after pro- 

 longed conservation of its solutions the following experiment 

 was conducted. 



On November 16, 1917, an extract from the stomachs of 

 thirty bees per 30 c.c. of a mixture of glycerine and water, 

 with the addition of 10 drops of toluol, was prepared. This 

 extract, preserved in a dark place at the temperature of the 

 room, was analysed in the usual way on November 17, 1917, 

 April 10, 191S, and October 15, 1918. The results obtained 

 from the analysis are represented in Table IX. 



The series of analyses given in Table IX shows that the 

 activity of invertase in solutions prepared in a mixture of 

 glycerine and water does not alter after being preserved for 

 at least eleventh months, in which respect invertase differs 

 markedly from catalase. 



Lipase. 



As is known, lipase belongs to ferments splitting fats into 

 fatty acids and glycerine. 



The source of fatty food for the bee is presented by propolis 

 which contains, according to the analysis of one of us (Zarin), 

 about 6 per cent, of fat. 



The question whether the fatty substances of propolis are 

 assimilated by the organism of the bee cannot be regarded as 



