46 LUMBRICUS TERRESTRIS. 



g) The clitellum, a saddle-like swelling occupying the dorsal and 

 lateral portions of segments thirty to thirty-six approximately. 

 The location varies considerably in different species. The degree 

 of development, also, depends on the conditions for breeding. 



h) The short locomotor setae arranged in rows along the ventral 

 and lateral surfaces. How many rows are there ? How many 

 setae on each segment ? Are there setae in the region of the 

 clitellum ? 



i) The slit-like openings with tumid lips on the ventral surface of the 

 fifteenth segment. These are the male reproductive apertures. 

 On the segment immediately in front are two minute openings, 

 the female reproductive apertures. These are seen with 

 difficulty. 



j) The capsulogenous glands lodged in the sacks at the bases of 

 some of the setae in the region of the reproductive apertures. Their 

 presence is indicated by local swellings. 



Exercise i. Draw the first forty and last twenty segments ventral 

 view on a scale of two. 



Technical Note. With a pair of fine scissors carefully slit the body wall, 

 along the mid-dorsal line from the prostomium to a point an inch 

 or so behind the clitellum. Sever the internal partitions attached 

 to the wall and spread the specimen open, pinning it to the cork in the 

 bottom of the pan. 

 INTERNAL ANATOMY. Note, further, the following: 



a) The transverse partitions or septa partially dividing the body 



cavity ccelome into a series of chambers. 



b) The pharynx, a muscular enlargement of the alimentary canal 



at the anterior end. 



c) The oesophagus extending from the pharynx to "d)." It will 



probably be hidden by other organs. 



d) The crop, a soft-walled sack occupying segments twelve to fifteen. 



e) The gizzard just back of the crop. It has firm walls and is light 



in color. 



