600 F. H. GRAVELY. 
paratrochs (“ Zwischenparatrochen,” Hicker). The band 
of a mesotrochal larva is called a mesotroch. 
The extension of the preoral lobe that often occurs in the 
plane of the prototroch in order to increase the extent of this 
important swimming organ is called the umbrella. 
In the Nereidiformia and some other worms there usually 
develop during the metatrochophore stage a number of seg- 
ments, definite for each species, all of which appear at about 
the same time and whose parapodia become very fully deve- 
loped before any further segments are added; the former 
(including the peristomial, but excluding the anal) are called 
primary, the latter secondary, segments. 
To this list of Prof. Hacker’s terms may be added the 
following, derived from the names of the three groups into 
which Claparéde divided his class ‘‘ Metachzetze ”’ (Polycheet 
larvee with provisional setae, see Claparéde 1863, p. 87); 
gastrotroch, a ciliated band extending transversely across 
the ventral surface of a segment; nototroch, a similar 
dorsal band; and amphitroch, a complete girdle of cilia. 
Finally, I have found it convenient to use the term neuro- 
troch for the tract of short cilia that often extends upon 
the ventral surface of the larva along the course of the 
nerve-cord, 
DrscrRiIpTION oF AN INTERESTING YOUNG SPECIMEN OF 
ODONTOSYLLIS SP. 
When towing a weighted net between Aldrick Bay (S. of 
Port Erin) and Gibdale Bay (Calf of Man), I had the good 
fortune to obtain a single young specimen of the brown 
Odontosyllis, frequently seen in the adult condition— 
occasionally accompanied by O. ctenostoma, and sexual 
specimens of Autolytus and Myrianida—swimming at the 
surface of the sea at the mouth of Port Erin Bay and further 
out towards the Calf on calm evenings during July. The 
genus Odontosyllis as defined by Langerhans (1879, p. 525) 
is characterised by the presence of distinct palps and of a 
