618 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
short capillaries, and separated from the dorsal tuft by a 
small conical process which precedes them in develop- 
ment. These parapodial structures are well shown in a 
mounted larva, of about 17 segments, which is 1,300y 
long by 38004 broad; many of the ventral setae have 
reached a length of 90”; they are smooth (?), stout, and 
slightly curved, and occur three or four to each tuft, the 
provisional setae being still present in the dorsal tufts. 
In another larva of about the same age most of the 
provisional setae have been shed from all segments (except 
the first) of the anterior half of the body, their place 
being taken by permanent dorsal setae resembling those 
of the ventral tuft in which the development of provisional 
setae appears to be entirely omitted. In this specimen 
crotchets are present in the ventral tufts of the thirteenth 
and succeeding segments; the gut is still full of opaque 
yolky material. 
These larvae probably belong to the same species as 
the “‘Larve mit riisselartiger Oberlippe” figured by 
Claparede (1863: Pl. VII., figs. 1-2) and briefly described 
in a foot-note to p. 86 of the same work. The unpaired 
dorsal (sensory ?) organ on the fore part of the head is 
indicated in his fig. 2. 
Another species of larva* showing the same remark- 
able modification of the head, and the same arrangement 
of the ciliated bands, occurs in the Plymouth plankton at 
the end of March and beginning of April. Many of the 
setae of this larva are very much stouter than those of 
Spionid D; some of them are smooth, and others serrate, 
the former presenting a variety of form strongly sugges- 
tive of the figure given by Hacker (1898: Pl. IIL., fig. 21) 
* These observations on Chaetosphaera were made after the above 
account of Spionid D had been written. As this paper in its original form 
is frequently referred to in my ‘Studies on Polychaet Larvae’ (Gravely, 
1909) it seems best to add this note rather than modify the original 
account. 
