I910.] J. STEPHENSON: On some Aquatic Oligochaete Worms. 237 
curve proximal to the nodulus is more marked, than in the 
anterior group of setae. The distal and proximal prongs of the 
fork are equal in length, the proximal! being 2 or 2} times as thick 
at its base as the distal, and both having a slight swelling near 
their base. The nodulus is equal on both sides of the shaft, and 
is situated distal to the middle in the proportion proximal : 
distale 3s Seasq. (Plexi. ie. 1p). 
The dorsai setae are regularly arranged in bundles of one hair- 
and one needle-seta. On one occasion a bundle of three was seen, 
composed of two needles and one hair. They begin in segment vi. 
The hairs are smooth, in length nearly or quite equal to the 
diameter of the body. The needles have a length of 56 +; the 
shaft is straight except in its distal third, where it is slightly 
sickle-shaped ; the end is ctenate, the outer prongs on each side 
are the strongest, the intermediate prongs are fine, and 2, 3, 4 or 5 
in number; some irregular forms were seen (fig. Id.e.f.). The 
nodulus is rather a slight angle in the shaft than a distinct 
swelling ; it occurs at the junction of middle and distal thirds 
(fig. Ic). 
Nais communis, Piguet, var. punjabensis. 
Three specimens were observed. 
In /ength they were about 2 mm. Segments of the one perfect 
specimen 26. The prostomium appeared shorter and more rounded 
than in the previous species, or than in perfect specimens as met 
with in Lahore; but I do not lay any stress on this, since this 
part may have been contracted in these specimens, or, which I 
think more probable, the individuals had only recently been 
separated,—perhaps separated spontaneously at the time of killing. 
The facts that, while the pharynx extended to segment v, the 
alimentary canal posterior to this showed no recognizable differen- 
tiation into oesophagus, stomach, and intestine; and that in one 
(stained) specimen the bvazm was much shorter from front to back 
than from side to side, I am inclined to explain in the same way ,— 
1.e., by supposing that the anterior part of the body had not yet 
completed its full differentiation. The eyes were laterally situated 
at the level of the mouth, were of moderate size, and of a deep 
purple colour; there were no ‘ Nebenaugen.’ 
The ventral setae of segments ii—v were 86 » in length, the 
shaft thinner than in those of posterior segments, and only slightly 
curved. The distal prong of the fork was 14 times as long as the 
proximal, the latter, on the contrary, being 14 times as thick at 
its base. The nodulus was slightly proximal (proximal : distal :: 
8 : 9); the swelling of the nodulus was slightly more marked on 
that side of the shaft which corresponds to the longer prong of the 
fork. (Fig. 2a.) 
Posterior to segment v the ventral setae were 70—75 p in 
length, with shaft moderately curved, and thicker than in the case 
of the anterior segments. The distal prong of the fork was very 
slender, only a little (up to 14) longer than the proximal, and 
