234 Records of the Indian Museum. [VoL. ¥, 
Signs of asexual multiplication were found frequently enough 
in the present specimens. There were no chains of two or more 
still unseparated animals; but a number of the individuals ex- 
amined had evidently been recently separated, as shown by the 
blunt or square, sometimes obviously lacerated prostomium, and 
the small size of the ventral setae of segments ii—v; these last, it 
may be said, are new productions in the zone of budding, and 
hence are when first developed smaller than those of the segments 
posterior to them. 
But unfortunately none of the specimens examined in the 
present instance showed any sign of sexual organs; and it is 
necessary therefore to fall back on other structures, and specially 
on the characters of the setae, in order to find marks capable of 
being used for purposes of diagnosis. As a matter of fact the 
current diagnoses of the known species of this and many other 
genera of the family are still based very largely on the setae; and 
the following accounts, though necessarily incomplete, have there- 
fore the merit of affording a possibility of comparison with 
previously described forms. 
The association between the worms and the sponge may be 
called a commensalism. <A similar phenomenon has been recorded 
by Annandale (Journ. and Proc. As Soc. Bengal, N.S., Vol. II, 
No. 5, 1906), who found a Chaetogaster (C. spongillae) living in 
association with Sfongilla cartert in Calcutta; in this case the 
commensal was only found in those parts of the sponge which had 
been killed or were dying, the healthy growing parts being quite 
free from them; Annandale accordingly supposes that it feeds on 
the organic débris left by the decay of the sponge. This supposi- 
tion appears to be not improbable, since Chaetogaster 1s carni- 
vorous,—exclusively carnivorous as far as I have observed the 
genus, I think; though Annandale (Journ. and Proc. As. Soc. 
Bengal, N.S., Vol. I, No. 4, 1905) speaks of having received from 
England a specimen in which the food probably consisted of 
diatoms and the like. The advantage to the Chaetogaster of a 
copious food-supply is obvious; there may also (Annandale, /.c.) 
be an advantage to the sponge in the liberation of the gemmules 
by the worm. 
So far as I have observed, however, the other genera of the 
Naididae are pure vegetable feeders, and hence the advantage 
which the forms now under discussion receive from association 
with the sponge would appear to be rather that of protection ; 
whether the advantage is altogether on their side, or whether they 
contribute anything in return, I am unable to say. 
Of the species of Nats described below, one (N. fectinata) is 
undoubtedly new ; but with regard to the others the question is 
not so simple. The form: with eyes resembles very closely that 
described by me (Memoirs Ind. Mus., Vol. 1, No. 3) as Nats 
variabilis, Piguet, var. punjabensis. At the time when I described 
this form, however, I had not. studied the genital apparatus, nor 
had Dr. Piguet published’ his account of the genital organs in 
