96 PHYSIOLOGY OF THE INVERTEBRATA. 



however, no action on fibrin. It contains sulphocyanates, 

 proved by the red colour produced by ferric chloride with a 

 drop of the secretion. The stomach of both the larva and 

 imago contains glandular follicles. These secrete a digestive 

 fluid, which answers in every way to that of a Vertebrate 

 pancreas. The Malpighian tubules are well-developed in the 

 imago, as well as in the larva of Pontia. Their function is 

 that of a renal organ, but this subject will be considered in 

 detail in our chapter on excretion. It may be stated in passing, 

 that according to Dr. B. T. Lowne, F.L.S.,* the Malpighian 

 tubules of Calliphora erythrocepJiala (the blow-fly) are 

 "hepatic "in function. If by hepatic he means that these 

 tubules have the function of a Vertebrate liver, his conclusions 

 are erroneous, for neither biliary acids nor glycogen are present 

 in these tubules. Again, if Dr. Lowne means by " hepatic " 

 that they have a pancreatic function, this is also erroneous, 

 because these tubules do not yield any digestive ferment or 

 ferments. On the other hand, the Malpighian tubules of the 

 Diptcra, including Calliphora, readily yield uric acid ; and 

 there is little doubt that they are physiologically the kidneys 

 of the animal ; although, concerning their place of develop- 

 ment from the alimentary canal, as well as from other 

 considerations, they are the homologues of hepatic organs 

 (liver). 



(c) The Hymcnoptera. — The structure of the alimentary 

 canal of Apis (the bee) has already been given. The long 

 stomach is furnished internally with small glandular follicles, 

 and by making an alkaline extract of the stomachs obtained 

 from a large number of bees (which had been kept for some 

 time without food), the extract contained a ferment which 

 hydrolyzes starch, and digests fibrin, although feebly. In 

 fact, it answers to the characteristic tests of trypsin or 

 pancreatin. An alcoholic extract of the bee's stomach does 



* The Anatomy, Flii/siolot/i/, Morphohyy, and Development of the Blow-fly 

 (1890). 



