264 Annals Entomological Society of America [Vol. XV, 



Phryganea interrupta Say* Plate XV, Fig. 11. 



In P. interrupta, the oesophagus passes through the head as a 

 narrow tube and enlarges toward the posterior margin of the prothorax 

 to form a crop of small dimension which is marked from the proven- 

 triculus by a slight constriction.^ The proventriculus occupies the 

 meso and metathorax in length and practically fills the whole of the 

 body cavity in this region, it presents the silvery surface as in the 

 other forms and the longitudinal and circular muscles are evident. The 

 posterior end of the proventriculus extends over into the first abdominal 

 segment and here is constricted suddenly and passes through this seg- 

 ment as a small tube about one-fourth the diameter of the proventriculus 

 in the mesothorax. This constriction is so long that the longitudinal 

 muscles of the proventriculus do not follow the tube but span the dis- 

 tance from the beginning of the constriction to the surface of the 

 mesenteron and can be seen as threads across the open space. f 



The mesenteron is the same as in the other .forms and passes over 

 into the intestine of the proctodeum in the sixth segment where the 

 Malpighian tubules arise. These do not always assume the same posi- 

 tions, which is further evidence of Marchal's theory on their mobility. 

 Marchal, 1892. The intestine extends through segments six and seven 

 and at the anterior margin of the eighth there is a constriction as the 

 intestine passes over into the rectum. The rectum gradually grows 

 smaller as it nears the anus. The anterior portion of the intestine has a 

 heavy musculature and the lower part is ridged longitudinally and these 

 ridges become more prominent in the rectum and form four longitudinal 

 columns which continue to the anus. 



HISTOLOGY OF THE ALIMENTARY CANAL. J 



In this work the writer has divided the material into two parts: 

 that dealing with cellular structure and that relating to the musculature 

 of the canal. The condition in H. anatis is taken as a basis of compar- 

 ison and where L. indivisus differs from the above the condition is noted 

 and illustrated in the figures. 



Buccal cavity: The cells are flat and small with small nuclei The 

 cavity is heavily lined with chitin 



* This third species is selected on account of its larger size. 



t A normal oesophageal valve occurs at the division between proventriculus 

 and mesenteron. 



I In the histological work, both hot Gilson's and hot Bouin's were used with 

 eciual advantage if the material was to be used at once. If more than a month 

 were to elapse before the material would be used, Bouin's was by far the better 

 fixative, as those in Gilson's softened rapidly. 



Much better results were attained by clearing in xylol than in cedar oil. 

 An infiltrati'on of not longer than nine hours, including the time in xylol and 

 paraffin, equal parts, at 52 degrees F., produced the material most easily cut. 



Staining in Delafield's haemotoxylin and counterstaining in aqueous ]/2% 

 eosin produced excellent results as a general stain. For muscles and epithelial 

 cells, iron haemotoxylin made clearer slides than the above. Paracarmine with 

 a counter stain of orange G. was especially adapted to digestive epithelial tissue in 

 L. indivisus. 



