Benham. — On Earthworms. 137 



The clitellum is saddle-shaped, covering segments 14 to 17 

 usually, though in some individuals it encroaches on the 13th 

 and 18th segments. Its ventral margin is a fairly distinct 

 ridge, in line with the ventral chaetae. It is true that sections 

 show (as in many other "incomplete" clitella) a glandular 

 thickening of the epidermis on the ventral surface, but this is 

 only very slightly thicker than the normal epidermis. The 

 intersegmental grooves and the ventral chaetae are perfectly 

 evident. 



Genital Pores.— The male pores are not evident externally, 

 but their position is indicated on the 18th segment by the 

 characteristic specialisation of the lower surface of this 

 segment, resulting in a prominent and thickened ridge on 

 each side, limiting and overhanging a depression, which is 

 deeper laterally below the ridge than in the middle of the 

 segment. The anterior and posterior boundaries of this 

 transverse depression are more or less prominent, so that a 

 somewhat rectangular pit is formed ; in this lie the microscopic 

 male pores, in the lateral deeper regions, in line with chaeta b. 

 The two oviducal pores occupy the usual position, in front of 

 and mediad of chaeta a. There are two pairs of spermathecal 

 pores, between segments 7/8 and 8/9 ; each is on a small 

 papilla— very distinct in the formol specimens — which in 

 reality belongs to the anterior margin of the 8th and 9th seg- 

 ments respectively, but as the papillae overlap the furrow they 

 appear to be intersegmental (as is the truth with regard to 

 the " intersegmentally " situated spermathecal pores in 

 other worms). " Tubercula pubertatis " are very characteristi- 

 cally developed — as oval intersegmentally placed glandular 

 areas, with well-defined margins, slightly depressed centrally, 

 and probably acting as suckers. There are tw T o preclitellian 

 and one postclitellian in position, situated at 11/12, 12/13, 

 and 19/20. In the eighteen mature specimens at my dis- 

 posal these three are universally present ; in three instances 

 the postclitellian is rather small, and in one case an addi- 

 tional tubercle exists at 20/21. In another individual an 

 additional preclitellian tubercle is present at 13/14. I shall 

 return to these papillae in discussing the specific value of the 

 worm. 



Nephridial pores commence only at the 13th segment, and 

 in line with chasta b. 



Internal Anatomy. 



The septa behind the segments 7 to 11 are much thickened 

 and infundibuliform, those at 6/7 and 11/12 less so, though 

 stouter than the following ; the normal posterior septa are 

 thinner than in most earthworms of this size. 



Alimentary Tract. — The gizzard is small, but highly mus- 



