1910] Alimentary Canal of Psychoda Alternata 307 



EXPLANATION OF PLATES. 



Plate XLIV. 



1. Alimentary canal in surface view. 



2. Longitudinal section of alimentary canal. 



3. Mouth parts. 



4. Anterior end of larva with alimentary canal and nervous system in situ. 



5. Longitudinal section through the anterior portion of the head. 



6. Transverse section through the anterior end of the pharynx. Plane of 

 section sloping slightly dorso-caudad. 



7. Transverse section through the median portion of the pharynx. Plane 

 of section sloping slightly dorso-caudad. 



8. Portion of the transverse section through the pharynx in the region of the 

 large lateral pharyngeal muscles. 



9. Transverse section through the caudal region of the pharynx. 



10. Transverse section through the anterior region of the esophagus. 



11. Transverse section through the anterior end of the esophageal valve. 

 Plane of section sloping slightly dorso-caudad. 



Plate XLV. 



12. Longitudinal section of salivary gland. 



13.. Transverse section through the middle of the esophageal valve. Plane 

 of section sloping slightly cephalad to the right. 



14. Longitudinal section of esophageal valve. 



15. A portion of longitudinal section of esophageal valve. 



16. Longitudinal section of cephalic end of esophageal valve showing a por- 

 tion of the blood space. 



17. Longitudinal section through the tip of the infolded portion of the esoph- 

 agus, showing chitinous spines. 



18. A portion of a longitudinal section through the region of the caecal gland. 



19. Cells with enclosed concretions, from the region immediately caudad of 

 the caecal gland. 



20. Longitudinal section through the region at which the concretion-bearing 

 cells give way to the large polygonal digestive cells. 



Plate XLVI. 



21. Transverse section of mid- intestine through the region of large polygonal 

 digestive cells. 



22. Longitudinal section through the region at which the polygonal cells 

 give way to the tall slender ones. 



23. Transverse section of mid-intestine through the region of tall slender 

 cells. 



24. Longitudinal section through the region of tall cells. 



25. Transverse section through the region at which the Malpighian vessels 

 join the alimentary canal. 



26. Longitudinal section through the same region. 



27. Transverse sections of Malpighian vessels. (a and b) Through the pig- 

 mented secretory portions, (c) through the basal reservoir. 



28. Transverse section of the ileum immediately caudad of the Malpighian 

 vessels, showing absence of circular and longitudinal muscles. 



29. Longitudinal section of the anterior portion of the ileum. 



