294 Aiiiials Entomological Society oj America [Vol. XI, 



The replacement cells are more or less triangular cells, 

 which lie at the bases of the functional cells, at irregular 

 intervals, wedged in between two of the cells. The nucleus is 

 large in proportion (it is almost as large as that of the active 

 cells), and there is ■ but relatively little cytoplasm, which is 

 non-granular and non-vacuolar. The nuclei stain a little more 

 deeply, and the particles of chromatin are a little coarser 

 than is the case with the nuclei of the functional cells. Three 

 replacement cells are shown in figure 11. 



Basement niembrane. A very delicate basement membrane, 

 on which both the functional and the replacement cells rest, 

 can be detected in well fixed preparations and is doubtless 

 present in all cases. 



Circular muscles. Striated circular muscle fibres surround 

 the mid-intestine, lodged in a continuous sheath of connective 

 tissue, which forms a complete tube around the canal. The 

 fibres are branched, and often interlace. 



Longitudinal muscles. The longitudinal muscle fibres lie 

 outside the circular muscle layer. There are about forty of 

 these fibres, which branch and interlace to some extent. 



THE SECOND DIVISION OF THE VENTRICULUS. 



Striated border. The striated border is not well developed 

 in this region, but is doubtless always at least feebly developed, 

 even when it is not apparent in sections. It is not even as 

 sharply separated from the cytoplasm as in the preceding 

 region. 



Epitheliitm. The columnar epithelium is composed of 

 cells which are comparatively much longer and more slender 

 than those of the preceeding region. On the free end the cell 

 outlines are less even and very irregular, instead of about equal 

 and straight. The •nuclei are of about the same size, but are 

 oval rather than round; the}^ are median, or slightly basal 

 if the secretion be abundant. 



The second division of the ventriculus is shown in figure 12. 



The secretion takes place in the same manner as before, 

 but much more actively and abundantly. It is of quite a 

 different chemical nature, for the cytoplasmic balls stain a light 

 pink with eosin, and are very granular. 



