90 WILLIAM BLA.XLAND BBNHAM. 



Digaster, &c. The intersegmental grooves in this region are 

 very deep and wide, and the setae, except those of the ventral 

 row, are not very evident. 



Behind the clitellum the body of the worm becomes much 

 narrower and retains this diameter to the end of the body. 

 The five somites immediately in front of the clitellum are very 

 short, and the diameter of the worm is here much smaller, but 

 in front of these it increases and retains the size of the clitellum 

 up to somite ii. Somites x, xi, xii, xiii are very conspicuous, 

 and are not annulated as are those immediately anterior to them. 



The setse are eight in each somite and are not in couples, 

 but they are arranged in such a way as to form fourteen rows 

 along the body. In describing this arrangement it will be 

 convenient to adopt M. Perrier^s plan which he used in the 

 case of Plutellus,^ of numbering the setse on each side. The 

 most ventral seta on each side will be called " seta 1,^^ whilst 

 the most dorsal will be called " seta 7.^' The series of " seta 

 1 " form a continuous line on each side of the ventral mid-line 

 throughout the body, but the remaining three setse (" 2, 4, 6,") 

 on each side of one somite alternate with the three setse ('"3, 

 5, 7 ") of the somite in front and of that behind (fig. 23) . In 

 this way we get the fourteen rows of setae. 



As will be best seen from the figures (23 and 24) the setse 

 of the two sides of one somite are themselves not symmetrical. 

 The setse 1 and 2 of one somite, or I and 3 of the next somite, 

 correspond to the ventral couple ofLumbricus, &c., and setse 4 

 and 6, or 5 and 7 to the lateral couple of the same Earthworm. 

 The setse are very small, being only about "55 mm. in length ; 

 they have the usual shape, but the distal and proximal regions 

 differ in length ; the distal (free) region is much shorter than 

 the proximal (embedded) region, and its extremity is more 

 strongly curved than in the ordinary setse of Lumbricus 

 (fig. 25). 



External Apertures. — I could find no apertures what- 

 ever, except the terminal mouth and anus. But by dissec- 

 tion I find that the nephridia open to the exterior by 



' ' Arch, de Zool. Exper. et gen.,' t. ii, 1873, p. 245. 



