POLYCH ZT LARVA. 613 
larva of twenty-two segments (total length 2,100z, 
breadth 150”) shows the setae very clearly (Pl. III., fig. 
33). Those of the (single ?) tuft on the first seoment 
reach a length of 4504, whilst those of both 
dorsal and ventral tufts on the second and _ third 
segments are not more than 804 long; the fourth 
and succeeding segments bear setae 3004 long, 
these being less numerous on the fourth than on the 
remaining segments; they are provisional setae that are 
shed from the anterior seements—with the exception of 
the first—before they disappear from the posterior ones. 
The provisional setae of the first segment disappear very 
soon, however, and those of the remaining segments con- 
tinue to be shed, from before backwards. The permanent 
setae become more numerous, and hooded crotchets make 
their appearance in the ventral tufts of setae on the 
tenth and succeeding segments, being most numerous 
near the posterior end. The branchiae and podal 
membranes develop in series beginning on the second 
chaetigerous segment. — 
My observations upon this larva in the living condi- 
tion were confined to the stage in which the tentacles, 
though present, are still rather short. ‘The usual Spionid 
characteristics of the anterior end (see above, p. 607) are 
present. ‘The prototroch extends along the bases of 
the tentacles. The head presents a crested appearance, 
as in the advanced stages of Sproned A. Gastrotrochs, 
broken into four equal sections, are present on every 
segment, with the possible exception of the first three 
as in “© Claparede’s larva” (see above, p. 609). The 
telotroch is incomplete dorsally, as in other Spionid 
larvae. The tentacles of this larva, as well as its slender 
vyermiform appearance and long provisional setae, show 
it to be undoubtedly a stage in the development of a 
