I9g10.]_ J. STEPHENSON: On some Aquatic Oligochaete Worms. 235 
N. variabilis. These gaps have since been filled up (Piguet, Rev 
Suisse de Zool., Tome 17, Fasc. 1, 1909; Stephenson, Rec. Ind. 
Mus., Vol. V, part 1); and Dr. Piguet, who has himself examined 
specimens of both forms, has (loc. cit., p. 200) come to the 
conclusion that my worm should be called N. communis, Piguet, 
var. punjabensis. I accept Piguet’s conclusion, and shall, there- 
fore, refer to the form in what follows under this latter name. 
The remaining specimens have no eyes, but here again there 
is an almost complete agreement in the characters of the setae 
with the last form and with the Punjab variety of N. communis. 
The question then is whether the presence or absence of eyes is of 
itself of specific value; and this point, as will be seen below, I 
have decided in the negative, giving this form varietal rank only, 
as var. caeca. I may add that Nais bretschert is also described as 
having or as wanting eyes. 
It is, however, noteworthy that specimens with well developed 
eyes and others in which they are completely absent should be 
found in such close association. It is at first sight tempting to 
suppose that, as in so many cases throughout the animal kingdom, 
so here, the exposure to light stimulates pigment formation and 
a life in darkness suppresses it ; the eyes of the Naididae are mere 
pigment spots, and hence on this supposition it would be those 
specimens which inhabited the superficial parts of the sponge 
whieh developed eyes, and those which lived in its deeper parts 
which failed to do so. It seems to me rather doubtful, however, 
whether the conditions in an ordinary mass of Spongilla cartert 
would be so different at the surface and in the interior ; and also 
whether the worms are so entirely sedentary as would be implied 
on this hypothesis. 
I have added, for purposes of comparison, a description of the 
setae of what I regard as a typical specimen of N. communis, var. 
punjabensis, from Shalimar Gardens near Jahore, which I examined 
during the course of the present investigation in order to satisfy 
myself of the amount of similarity or difference between these 
several forms. 
Pristina longiseta, Elrbg. 
One specimen only was seen. This was an extremely well 
marked example; the ‘ proboscis’ measured ‘175 mm. in length, 
while one of the characteristic elongated dorsal setae of the third 
segment was over half a millimetre (54 mm.) in length, and thus 
reached far beyond the extremity of the proboscis. 
It seems doubtful whether this animal could have been living 
within the sponge. The enormously elongated setae just men- 
tioned could there have had no free play ; they would have much 
impeded the animal’s movements, and would probably very soon 
have been broken off. The fact that only one example out of 
thirty-eight was of this species is also, I think, significant. This 
one specimen was not improbably merely crawling on the surface 
of the sponge at the time it was taken. 
