Alimentary System of Gryllotalpa australis. 125 

 Physiological Notes. 



Perhaps no one has done so much experimental work to 

 explain the functions of digestion and assimilation in insects as 

 Plateau, and I regret not having had an opportunity of reading 

 all his papers. I am indebted to the writings of Miall and 

 Denny (3), and also to those of Cuenot (2), for summaries of 

 his work, and to the latter for a resume of the researches of 

 other notable workers and of his own. It is generally accepted, 

 I think, that the digestion of starch and sugar is etfected in the 

 crop by secretions from the salivary glands ; that the secretions 

 of the cells of the middle intestine, (those of the cieca playing a 

 predominent part), transform the albuminoids into peptones, and 

 also that fats are emulsified there. 



I can find no proof that there is any secretion to split fats into 

 fatty acids and glycerine outside the cells. 



Difference of opinion exists as to where absoi'ption and assimi- 

 lation take place. Plateau and Jousset de Bellesme state that 

 absorption takes place in the crop, the middle intestine, and 

 even part of the terminal intestine. Cuenot (2) states that it 

 is improbable, considering our present ideas on osmosis, that 

 there can be the least absorption into the crop and terminal 

 intestine, for both of them are covered by an impenetrable 

 chitinous cuticle.^ He further states that in the middle intes- 

 tine alone and its diverticula, all the absorption is carried on, 

 viz., that of the soluble products, peptones, glucose, and also fats. 



For the purpose of determining this, I made some experiments, 

 which prove that osmosis can take place, both in the chitinous 

 lined crop and terminal canal. 



To demonstrate this 1 employed the following methods : — 



On three separate occasions I exposed the alimentary canal, 

 and carefully ligatured it, 1st, at the commencement of the mid- 

 terminal canal, and 2nd, at the posterior end, just anterior to the 

 entrance of the ureter; also the oesophagus, at places, to close the 

 passages to and from the crop. I then cut away the closed mid- 

 terminal canal, and also the crop, and suspended them in a 5 per 

 cent, solution of magnesii sulphas for two hours, after which, one 

 at a time, they were thoroughly washed in three separate basins of 



1 Loc. cit., p. 306. 



