STUDIES ON POLYCHAT LARVA. 603 
The parapodia of the next twelve segments show in addition 
a broad dorsal ramus, supported by a shorter and more 
distinctly curved aciculum than is present in the longer 
ventral ramus, which ventral ramus resembles the only ramus 
of the anterior parapodia. The dorsal ramus bears a tuft of 
very long slender capillary setz, exactly like the special 
natatory sete that are found in this position in sexually mature 
specimens of this and many other Syllids. Finally, at the 
posterior end of the body there are two chetigerous segments 
devoid of the dorsal lobe and natatory set, and evidently not 
yet fully developed, the tissues taking a deeper stain, and the 
tuft of compound setz being shorter (especially in the ter- 
minal one) than in the segments preceding them. 
The gut is fully differentiated, and divided into pharynx— 
in which, however, I have been unable to detect any teeth, 
although De Saint-Joseph figures all six of them in a much 
younger (five-segment) larva which he refers to Odonto- 
syllis gibba (1886, Pl. VIII, fig. 40)—gizzard, and intes- 
tine, the last bemg deeply constricted between the seg- 
ments. 
The body is covered externally with minute particles of 
some highly refractive foreign substance—possibly caught 
simply by the mucus that these worms not infrequently exude 
under the action of the fixing agent. 
Tt will be seen from this description that we have here a 
Syllid in which true biramous appendages appear at a very 
early age. These are strictly comparable to those found in 
the mature form, occurring on precisely the same segments 
so far as the development of these permits, and showing 
precisely the same structure. It seems reasonable to suppose, 
therefore, that they are present throughout life, and from 
this it may be concluded that the species is permanently 
pelagic. So far as I know it has never been dredged up 
from the bottom, but so little work has as yet been done 
upon the Polycheet fauna of the Port Erin district that the 
only definite information to be had in regard to this species 
is that it is to be found swimming at the surface on calm 
