392 MARGARET LEWIS NICKERSON. [Vol. XVII. 



Summary. 



1. The sensory nervous system of Phascolosoma Gouldii, 

 posterior to the tentacles surrounding the mouth, is to be found 

 entirely in the epidermal bodies distributed abundantly through- 

 out the body of the worm and in the nerve fibers connecting 

 them with the central nervous system. 



2. These epidermal bodies may be grouped into two classes, 

 and each class into two types. One class contains gland cells ; 

 the other is non-glandular. The second type of glandular 

 organ may be distinguished from the first by the presence of 

 intracellular sacks and canals in the gland cells. The second 

 type of non-glandular organ is distinguished from the first by 

 the possession of a bulb-like structure projecting above the 

 general level of the cuticula. 



3. All four types of epidermal organs possess sensory cells. 



4. Nerve fibers are never found in continuity with the gland 

 cells of either type of glandular organ, though the contrary 

 has been several times asserted by different investigators. 



5. The sensory cells of all these organs are bipolar in shape, 

 the cell body in the non-glandular organs being larger than 

 that in the glandular organs. 



6. Each of the peripheral processes of the sensory cells ends 

 in a delicate sensory hair, which, in some cases at least, is pro- 

 longed beyond the surface of the cuticula. In one type only, 

 the second type of the glandular organs, the exact form of the 

 peripheral ending was not made out. 



7. The central processes of all these sensory cells enter the 

 large nerves passing from the ventral nerve cord. 



8. One type of glandular organ possesses a very remarkable 

 structure consisting of a communicating set of intracellular 

 canals, each canal leading from an otherwise closed pouch. All 

 these communicating canals finally open to the surface of the 

 worm through a common duct. 



9. The peculiar sacks or pouches belonging to these glandular 

 organs are reservoirs for the secretion from the gland cells 

 and show much variation in size and appearance in correspond- 

 ence with the phases of functional activity of the cells. The 



