1878.] A Lesson in Comparative Histology. 345 
Fig. 1 of the plate represents a longitudinal section through 
a whole grasshopper, magnified three times. The cavity of the 
mouth, M, is not very large. The first segment of the digestive 
canal extends through the head and thorax, and is composed of 
two divisions, the narrow cesophagus, Oe, and the enormous crop, 
which is itself formed of two parts, an anterior, (71, with trans- 
verse, and a posterior, C°, with longitudinal ridges; this last 
terminates in a narrow portion, P, which corresponds to the 
proventriculus of other insects. This segment of the alimentary _ 
canal is especially characterized by its thick and hard cuticula, 
which almost completely obscures the underlying epithelium, 
outside of which, however, there is a powerful coat of muscular 
fibres of the kind called striated. The cuticula is thrown up 
into ridges and armed with fine but sharp spines that point back- 
wards. The obvious function of these parts is to grind up the 
food: they are organs of mastication. The features in question 
are well shown in Fig. 4 of the plate, which represents a trans- 
verse section through the posterior part of the crop, magnified 
forty-five diameters. The ridges, id, are small and numerous, 
and upon them can be seen the little spines, s s, and they are 
covered by the cuticula, which is very thick. The epithelium 
does not appear distinctly by this magnification, nor do the longi- 
tudinal muscles, Z, but the transverse or circular muscles form a 
very thick layer, muc. C. Where the ridges are transverse, as in 
the front part of the crop and the cesophagus, we find the trans- 
verse muscles less developed and the longitudinal the most 
powerful. 
The middle segment of the alimentary canal consists of the 
large ventricle, vex, known in German as the “ Chylusmagen,” 
with six blind sacks or diverticula appended to its anterior 
extremity; only one of these, however (Dzv), appears in the sec- 
tion Fig. 1. In this segment the cuticula is very delicate, but the 
epithelium undergoes another kind of modification, being thrown 
up into folds. In the diverticula there are twelve longitudinal 
folds, the structure and arrangement of which can best be seen in 
a transverse section colored with hematoxiline, Fig. 8, Plate II. 
The folds are high and thin, and covered by the epithelium, which 
is everywhere of about the same height. Outside there is a thin 
layer, muc, of muscular fibres, which do not enter into the com- 
. Position of the folds, Between the muscles and the epithelium 
