DIGESTIVE SYSTEM. 69 



effectually prevent the passing upwards of any solid 

 particles, such as pollen grains, whole or broken, 

 even could the difficulties previously mentioned be 

 overcome. 



But it will be seen that these explanations are 

 partly negative, giving us no reason for the presence 

 of either tube extension or down-pointing bristles, since 

 a mere sphincter (or ring of closing muscles) would, 

 by contraction and relaxation, have either totally pre- 

 vented regurgitation, or permitted it, if necessary, and 

 also have enabled the bee to take such food from 

 the honey sac as it might at the time being contain. 

 It is clear, then, that either parts have been added 

 which are not requisite, or that some function exists 

 which has hitherto escaped observation. Surely it is 

 the latter. Dissecting bees from the hive, young and 

 old, ordinary nurses and queen grub feeders, starved 

 and fully fed, gave me no help in this matter, beyond 

 showing the extraordinary complexity and variety of 

 movement of which the stomach-mouth is capable ; 

 but those that were engaged in gathering yielded the 

 solution. 



On the Compositae, as well as many other orders, 

 bees suck up nectar, in conjunction with much 

 pollen, and, examining the honey sac of one work- 

 ing upon a single dahlia, e.g., the outside wrinkled 

 membrane (sm, A, Fig. 14) is seen to continually run 

 up in folds, and gather itself over the top of the 

 stomach-mouth, bringing with it, by the aid of its 

 setae, the large pollen grains the nectar contains. 

 The lips (/, I, B, Fig. 14), now opening, take in this 

 pollen, which is driven forwards, into the cavity made 



