Alimentary Sysfe^ni of Grylloi<ilpa auatraUf^. 127 



and remains for a long time. (In fasting insects 

 after two months, and may be longer, I have 

 found food material there and numberless bacteria). 

 The required soluble products are then selected 

 and absorbed by the epithelial cells, to be passed 

 on to the blood plasma, the setaceous villi and 

 folds playing a large part in gathering what 

 would otherwise escape, while the blood cells 

 within the crypts may absorb, assimilate and 

 transfer the products to other parts. 

 5. The insoluble residue passes on to the rectum, where 

 mucus, secreted by the cells of the longitudinal 

 rectal glands, is mixed with it and the contents 

 ejected. When an insect is alarmed the black 

 viscid contents of the rectum are ejected with 

 considerable force to serve in defence. The bac- 

 teria, which always exist in large numbers in the 

 mid-terminal canal, may render important service 

 in the breaking up of albuminoids, proteids and 

 fats, which have escaped digestion in the mid- 

 intestine (cfeca). 



LITERATURE REFERRED TO. 



1. Bordas. — L'Appareil digestif des Orthopteres. Ann. So. 



Nat., t. v., 1897, pp. 1-224. 



2. Cuenot. — Etudes physiologiques des Orthopteres Arch. 



Biologie, t. xiv., 1896, pp. 293-341. 



3. Miall and Denny. — The structure and life-history of the 



Cockroach. London 1886. 

 For full lists of literatui*e see the valuable text-book of 

 Entomology by Prof. A. S. Packard (Macmillan), 1898. 



EXPLANATION OF PLATES. 



Note. — With the exception of Figs. 1 and \a, all the Figures 



have been outlined under a camera lucida. 



Fig. 1. — Semi-diagrammatic view of the enteric system of 

 Gryllotalpa australis (Erich.), dissected from the 

 left side, and showing positions of the various 



