ie. 
POLYOCH AT LARVA, 617 
This snout appears to be formed from the anterior margin 
of the head and lips, and is a peculiar modification of the 
cephahe larval organs characteristic of the Spionidae.* 
Sections have revealed the presence of a curious 
(sensory ?) organ, situated on the fore part of the head 
in the mid-dorsal line immediately above the brain. 
Behind this are situated the eye-spots, which are of a 
reddish colour and somewhat opaque. 
Nototrochs are absent. The gastrotrochs of the 
anterior segments are as usual modified in connection with 
the special structures of the head. The fourth and 
succeeding segments, however, each bear laterally an 
inner and outer paw of short rows of extremely powerful 
100 cilia on the ventral surface; whether any cilia were 
present nearer to the middle-line it was impossible to 
determine on account of the extreme opacity of this 
region in the larvae examined. These gastrotrochs 
became smaller and finally disappeared altogether 
towards the posterior end of the body. The cilia of the 
telotroch were much longer than those of the prototroch, 
the former being 120 long, the latter only 604. The 
tentacles develop at a very early stage, and the prototroch 
extends along their bases (Pl. III., figs. 36-37, Pér.). 
The gut consists of a muscular pharynx followed by a 
broad intestine which is filled with a very opaque yolky 
material; the walls of the gut often contain dense black 
pigment. 
The provisional setae are very stout and distinctly 
eurved. Those of the first segment reach a length of 
300%, those of the remaining segments a length of 200p ; 
they are confined to the dorsal lobe of each parapodium, 
and appear before the parapodia begin to project from 
the body-wall. The ventral setae develop later; they are 
* It has been deseribed elsewhere (Grayely, 1909). 
