THE PROVENTRfC'ULUS A STRAINER 311 



forwards into the chyle-stomach, the tube extension, whose necessity now 

 becomes apparent, prevents the pellets forming into plug-like masses just below 

 //, IM-. 313, for, by the action of the tube, these pellets are delivered into the 

 midst of the fluids of the stomach, to be at once broken up and subjected to the 

 digestive process. And third, while the little gatherer is flying from flower to 

 flower, her stomach-mouth is busy in separating pollen from nectar, so that the 

 latter may be less liable to fermentation and better suited to winter consump- 

 tion. She, in fact, carries with her, and at once puts into operation, the most 

 ancient, and yet the most perfect and beautiful, of all 'honey-strainers.' " 



Forel's experiments on the proventriculus of ants prove that through its 

 valvular contrivance it closes the passage from the crop to the mid-intestine 

 ("chylific stomach"), and allows the contents of the former to pass slowly 

 and very gradually into the latter. Emery confirms this view, and concludes 

 that the organ in the Camponotidge and in the Dolichoderidse provided with a 

 calyx-bell, usually regarded as a triturating stomach (Kaumagen), but more 

 correctly as a pumping stomach, consists of parts which perform two different 

 functions. Under the operation of the muscles of the crop the entrance to the 

 pumping stomach becomes closed, in order by such spasmodic contraction to 

 prevent the flow of the contents of the crop into the proventriculus. By the 

 pressure of the transverse muscles of the proventriculus its contents are emptied 

 into the mid-intestine, while simultaneously a regurgitation into the crop is pre- 

 vented. In the Dolichoderidse and Plagiolepidinse the closure in both cases is 

 effected by the valves. In the true Camponotidse there are two separate con- 

 trivances for closing ; the calyx belonging to the crop-musculature, while the 

 valves essentially belong to the proventricular pumping apparatus. 



Opinions vary as to the use of this portion of the digestive canal. Graber 

 compares it to the gizzard of birds, and likens the action of the rosette of teeth 

 to the finer radiating teeth of the sea-urchin, and styles it a chopping machine, 

 which works automatically, and allows no solid bits of food to pass in to injure 

 the delicate walls of the stomach (mid-gut). 



He also states that the food when taken from the proventriculus is very finely 

 divided, while that found in the oesophagus contains large bits. 



Kolbe says that this view has recently been completely abandoned, and that 

 the teeth are used to pass the food backwards into the chylific stomach. "But 

 Goldfuss had denied the triturating action of the proventriculus of the Or- 

 thoptera (Symbolse ad Orthopterorurn quorundam CEconomiam, 1843), stating 

 that the contents of the same are already fluid in the gullet, so that the fore- 

 stomach (Kaumagen) does not need to comminute the food " (Kolbe). In the 

 Gryllidse and Locustidse, just before the posterior opening of the proventriculus 

 into the stomach the chitinous lining swells into a ring and projects straight 

 back as the inner wall of the cylindrical chylific stomach. The muscular layer 

 forms two sac-like outgrowths or folds, which separate on the circular fold 

 from the chitinous membrane. This apparatus only allows very finely com- 

 minuted food to pass into the stomach. 



In the Acrydiidse (Eremobia muricata} at the end of the proventriculus, 

 where it passes into the stomach, is a small circular fold which hangs down 

 like a curtain in the stomach. 



The oesophageal valve. Weismann l states that the origin of the 

 proventriculus in the embryo of flies (Muscidse) shows that it should 



1 Weismann, Die nachembryouale Entwicklung der Musciden. Zeitschr. fur 

 wissen. Zoologie, xiv, p. 196, 1864. 



