Almientary System of Grylloialpa australis. 117 



The annular muscles of this portion of the canal are more 

 numerous than in the fore-gullet, and the wall is consequently 

 not so distendable. 



The cuticule is raised into more decided longitudinal anticlinal 

 folds, and the whole is fringed by long fine chitinous setee, 

 pointing backwards ; very different in structure from those of 

 the fore-gullet. 



Ppoventpiculus op Gizzard. 



The Proventriculus or gizzard is spheroidal in shape, and 

 measures about 3-5 mm. through its long axis. It is united 

 with the posterior end of the hind-gullet, leading from the crop. 

 At the orifice the walls of the food-canal are raised into definite 

 cushions, which unitedly act as a valve to close the gizzard and 

 prevent a retrograde movement of the food. 



The outer wall at the hinder extremity is I'eflected and joins 

 with two csecal organs (the mid-intestine) ; the inner chitinous 

 layer is continued to form four membranous curtains, the oesopha- 

 geal valve of Weismann, which hang loose and function as guards 

 to prevent the entrance of coarse food material into the cfeca. 



A median transverse section of the gizzard (Fig. 4) reveals the 

 presence on the outside of {a) a very thick layer of annular 

 muscle fibres, underlying which are ((5) longitudinal muscle fibres 

 comparatively few in number ; {c) a basement membrane, on 

 which is situated {d) a layer of chitinogenous cells, which secrete 

 varying thicknesses of chitin, forming strong and elaborately 

 shaped teeth and setse. The teeth are situated upon folds of 

 the inner wall, and they form six definite columns, each column 

 being similar in structure. Each column is transversely divided 

 as far back as the radial wall by generally fourteen or fifteen 

 definite, but irregular radial ridges, which are disposed longi- 

 tudinally one underneath the other, and separated by very short 

 distances (Fig. 3). 



The appearance of a transverse section of the gizzard, showing 

 one of these columns cut across, with the upper or anterior 

 surface of one-sixth part of a radial ridge uppermost, is shown in 

 Fig. 4. Each part of the ridge is similar ; it will be unnecessary 

 to describe more than one to represent the whole. They are 

 each bilaterally symmetrical. A central fold projects into the 



