POLYCH ALT LARVA. 621 
anterior margin of the head. Hus larvae are certainly 
not specifically identical with the Port Erin ones 
however, and whether these structures are also present in 
them is yet to be ascertained. The first segment of the 
Port Erin larvae is longer than any other and bears a pair 
of tufts of long (850), stout, curved, ringed setae (PI. II., 
fig. 31), with a short parapodial process in connection 
with each. The remaining intertrochal segments each 
bear a discontinuous transverse band of black pigment. 
They are usually devoid of setae; but in one larva a 
single pair is present on the fifth (?) segment; these two 
setae are much shorter and more slender than those of 
the first segment, and they appear to be quite smooth. 
Claparéde figures ringed setae on all segments in his 
5-seement stage (loc. cit., fig. 6), those of the four 
posterior segments being about half the length of those 
of the first seement; he also figures the pigment as a 
stellate patch on each side of the four posterior 
intertrochal segments, and not in transverse bands as in 
the Port Erin larva. . 
Nectosoma.—tTwo species of Polydora have 
been found in the nectosoma stage. One of these 
(described under the name “ Polydora B”’) bears pigment 
arranged, roughly, in transverse bands (see fig. 32); it is 
possible that this may be a later stage of the 
Metatrochophore above described, but as all the specimens 
obtained show 15-20 chaetigerous segments it is impossible 
to find any certain evidence of this. The other species 
is much commoner and is characterised by stellate 
pigment-patches, arranged in a row down the middle of 
the dorsal surface of the body. As much more complete 
series of these larvae have been found it will be 
convenient to describe this species (to be referred to as 
Polydora A) before the other. 
