POLYCH AT LARVA. 601 
NoPE typ Da (el i hes.) 10; 10): 
One of the commonest Polychaet larvae in the Port 
Kirin plankton during July resembles closely in form and 
setae the well-known larvae of Nephthys, to which genus 
I have no hesitation in referring it. The examination 
of the living larvae was, however, insufficient, and I 
cannot give as complete an account of them as of some 
others. This examination was, moreover, confined to 
larvae in the nectochaeta stage, the metatrochophore 
stage being seen after fixation only. 
Metatrochophore.—the youngest larvae seen 
are pear-shaped and 500 in length by 3504 greatest 
breadth, this coinciding with the position of the proto- 
troch. The mouth is certainly surrounded by short cilia. 
The lateral masses of nervous tissue in the preoral lobe 
are well developed, and the walls of the oesophagus are 
much thickened, but not pouched as in Polynoé larvae. 
The body shows a posterior unsegmented region and 
seven primary segments (PI. III., fig. 10), which as yet 
ean hardly be said to bear appendages, though in 
segments 2-7 it is just possible to distinguish lobes 
representing neuropodium and notopodium, setae being 
just visible in the former, but barely projecting beyond 
the soft tissues. <A telotroch is present. 
During the second metatrochophore stage the 
umbrella is reduced to about 254 diameter, and the 
appendages (with their setae) develop from before back- 
wards, except for those of the peristomial segment, which 
arise much later than those of the second segment. 
Nectochaeta.—tThis stage may be said to 
commence when the setae of the peristomial segment 
appear. ‘The umbrella, as noted above, is now only 25" 
in diameter, i1.e., very little broader than the rest of the 
body. ‘The prototroch consists of an anterior row of short 
