202 bulletin: museum of comparative zoology. 



7. The blood supply of the organ is from the antennal and sternal 

 arteries. 



8. The nerve supply is from the antennal nerve. 



9. The endsac encloses a single chamber with numerous radiating out- 

 pocketings ; the labyrinth is a complicated mass of anastomosing tubules, 

 which are short and of varying calibre. 



10. The epithelial cells of endsac and labyrinth are of distinctly differ- 

 ent types, and there are no cells of an intermediate nature. 



11. The cells of both endsac and labyrinth take part in the secretion. 

 This is in large measure given off in the form of globular vesicles con- 

 taining an irregular granular mass or clot ; these are constricted off from 

 the free ends of the cells. 



12. The wall of the vesicle is made up of a single layer of epithelium 

 without folds, surrounded, except on the ventral side, by a muscular 

 sheath, which is variable in thickness. It is presumably by the con- 

 traction of this sheath that the secretion is forced out of the external 

 orifice of the duct. Between the epithelial and muscular layers there is 

 a vascular layer. 



13. The endsac arises from the mesoderm occupying the axis of the 

 second antenna, when the embryo is 15 to 17 days old. At first there 

 are but one or two cells differentiated. 



14. By nuclear division without corresponding formation of cell walls 

 there is formed a solid multinuclear body, — a syncytium. 



15. Vacuoles appear in the syncytium and probably by confluence form 

 a single large vacuole. 



16. The belated cell walls form around this vacuole, so that the vacuole 

 becomes an intercellular space, — the lumen of the endsac. 



17. The ectodermic ingrowth — which in the adult becomes the laby- 

 rinth — occurs on the median ventral face of the antenna, and appears 

 when the embryo is 28 to 30 days old. 



18. This ingrowth passes, first, proximad and then around the anterior 

 side of the endsac; by separation of its cells a lumen is formed near its 

 deep end. 



19. The separation of cells progresses rapidly toward the exterior, 

 which is reached by the end of the sixth week. The lumen thus formed 

 becomes the permanent duct and the lumen of the labyrinth. 



20. The lumina of the endsac (mesodermic) and of the ectodermic 

 sac (labyrinth) do not become continuous until the embryo is 273 to 

 303 days old. 



