ANATOMY OF THE EARTHWORM. 261 
posterior extremity, a considerable amount of resistance is 
experienced, in consequence of a roughness of the worm’s 
skin. This roughness is owing to the presence of minute sete, 
of which there are four pairs on nearly every ring of the 
worm’s body, those only comprised by the cingulum and the 
smallest anal segments being free from them. Two pairs of 
the sete have a ventral aspect, and a pair on either side are 
disposed laterally (fig. 8). One of these setz placed beneath 
the microscope shows a slightly curved form, is transparent, 
of a yellow colour and fibrous structure (fig. 7). The broader 
portion is fixed in the integument, and is softer than the 
exposed portion. 
The setz are secreted by very minute glands, of which there 
are four in every segment, each situated in connection with the 
inserted portions of a pair of setze, These setigerous glands 
may be seen in fig. 11,4, d. In acertain part of the body the 
setigerous glands often acquire a large size, and their normal 
function appears to become subservient to some other. Large 
semi-developed sete are thus found im them, as also a viscid 
secretion, the function of which must be discussed in connec- 
tion with the reproductive system. The sete are very fre- 
quently lost or injured in use by the earthworm, and their 
place left unsupplied. From this we may conclude that the 
process of their formation is not rapid, nor adapted to sup- 
plying a vacancy immediately on its being required ; but, 
rather, a regular and slow development, which takes place 
equally, whether injury has been sustained or not, and irre- 
spective of wear. Another feature of the integument which 
will be noticed by the most casual observer is its enlarge- 
ment into the “cingulum,” extending from the twenty-ninth 
to the thirty-sixth segment. The cingulum, which, though a 
tegumentary appendage, is strictly an accessory organ of re- 
production, is of a paler colour than the rest of the integu- 
ment, encloses the dorsal and lateral surfaces of the rings 
over which it extends, but is not developed from the ventral 
surface. The structure of this body is glandular, being com- 
posed of a great number of minute pyriform papille, which 
secrete a fluid, and also act as adhesive organs during the 
congress of two individuals. The epidermis covering the 
papille is remarkably thin, and appears to be ruptured when 
coition occurs. In examining the ventral surface of the 
worm various minute apertures will be discovered in the 
anterior segments of the body; but as they are intimately 
connected with certain of the organs of reproduction, I defer 
describing them for the present. ; 
