No. I.] SENSE-ORGAA'S OF LUMBRICUS AGRICOLA. 197 



are at right angles to those of the other layer, and the fibres of 

 both layers are at an angle of 45° to the long axis of the body. 

 The inner surface of the epidermis rests on a thin basement- 

 membrane, which is apparently composed of connective tissue 

 and separates the epidermis from the circular muscle-layer 

 beneath. The epidermis itself is composed of two layers of 

 cells, a superficial and a basal layer, each one cell deep. The 

 cells of the superficial layer are of two kinds, supporting cells 

 and gland-cells. A supporting cell is almost columnar in form ; 

 it has a square-cut top, a base prolonged into several processes, 

 and an oval nucleus at about the middle of its height. A gland- 

 cell is "goblet-shaped." It has an external opening through a 

 pore in the cuticula above it for the discharge of its secretion, 

 and the nucleus is usually forced into the base of the cell by 

 the accumulation of the secretion. The base is sometimes 

 broad and entire, and sometimes divided into basal processes. 



The cells of the basal layer are imbedded between the basal 

 processes of the cells of the superficial layer. A basal cell is 

 usually rounded and contains a rounded nucleus ; sometimes it 

 extends toward the cuticula for a varying distance between the 

 cells of the superficial layer. Most writers state that the sup- 

 porting cells are probably changed into gland-cells, but Cerfon- 

 taine ('9o) believes that both supporting and gland-cells are formed 

 from these basal cells. Intermediate stages between the basal 

 cells and both kinds of superficial cells are so easily found as 

 to leave in my mind no doubt as to the correctness of his state- 

 ment. All the cells of the basal layer rest directly on the 

 basement-membrane. All the cells of the superficial layer 

 which do not rest directly on this membrane reach it by means 

 of their basal processes. (See Cerfontaine ('SO) for figures of 

 these various cells.) Imbedded between these various kinds of 

 epidermal cells are groups of sensory cells collected into definite 

 sense-orzans. 



The sense-orgajis of the epidermis. — The sense-organs in the 

 anterior metameres have been studied as a type (PI. XIII, Fig. 

 i). Each organ has in general the form of an ovoid, the smaller 

 end of which projects into a raised spot in the cuticula above 

 it; the broader end is flattened, and rests on the basal mem- 



