268 WILLIAM BLAXLAND BENHAM. 
three or four, one of the annuli being sometimes subdivided. 
It was by tracing the nephridiopores that it was possible to as- 
certain the limits of the somites. The sete are much too minute 
to be of any assistance, as they are extremely difficult to see, 
whilst the nephridiopores are very evident. By this means, 
and subsequent dissection, I have drawn up the following table. 
I count the first nephridiopore as being in the first annulus of 
somite II. 
Somite I consists of 3 annuli (exclusive of the prostomium). 
33 II 3) 7 33 
39 Taik 39 6 3” 
33 IV bE 7 ” 
39 v bE] 6 93 
29 VI 3° 6 33 
” VII 9 6 39 
» VIII cs Ay es 
33 IX ” 3 39 
39 xX 3 3 39 
and in all subsequent somites 3, 
Whether these numbers are constant for every individual I 
cannot say. 
There is a great thickening of the body in somites rv, v, VI, 
vir, due to the thickness of the muscular layers of the body wall, 
more especially to that of the longitudinal muscles. 
The clitellum is very noticeable on account of its green 
colour; it is further forwards than in Lumbricus. It extends 
over the somites xi1I to xxv inclusive. (Pl. XV, fig. 1). Its 
boundaries, however, are not very distinct, since both anteriorly 
and posteriorly it merges into the neighbouring somites ; it 
does not extend completely round the body, as is the case in 
Pericheta, but resembles that of Lumbricus. In histological 
structure it differs somewhat from the latter Earthworm, as 
will be seen below. 
Setz.—The sete are arranged, asin Lumbricus, in four 
couples in each somite, the two sete forming a couple being 
very close together. One pair of couples is quite lateral (s. /.) 
the other pair latero-ventral (s.v.). (Plate XV, fig. 1 and 10). 
The sete are very minute, whence the name of the genus 
