POLYCHET LARVA 627 
the gills show that Claparéde’s larva cannot, however, be 
of the same species as Agassiz’s, and Leschke (1903: pp. 
118-121; Pl. VI., figs. 1-6), who has described the 
development of P. ciliata from the egg, states that the 
larva of this species resembles those described by 
Agassiz. The early stages described by Leschke, more- 
over, differ markedly from those described by Claparede, 
in that the Trochophore bears no setae at all, a stage 
with the rudiments of three intertrochal segments 
(ieschke, loc. cit.: Pl. VI., fig. 4) bearing short setae, 
which only reach their full dimensions in the stage with 
three completely developed segments (loc. cit.: Pl. VI., 
fig. 5). Claparéde himself accepted Agassiz’s removal of 
his “Leucodora’’ larva from the genus Polydora 
(=Leucodora), and in conjunction with Meecznikow 
described another larva (1869: p. 175; Pl. XIL., fig. 3) 
as that of Polydora. But the difference between this 
larva and Agassiz’s is far greater than that between his 
original “Leucodora”’ larva and the latter; and a 
comparison between his figure of it, and Pl. IV., figs. 41, 
_ 42, and 434 of the present paper will prove at once that 
it is really the larva of Pectinaria, and that the special 
setae supposed to belong to the fifth segment are in 
reality the paleae of this worm, which develop internally 
in the position shown, and appear fully formed at the 
anterior end during metamorphosis as described below. 
De Saint-Joseph (1894: pp. 63-4; PI. III, fig. 73) 
describes a larva which he says is identical with Agassiz’s 
larva of P. ciliata. The larvae figured by Cunningham 
and Ramage (1887: Pl. XXXVII., figs. 21, 2J) as 
advanced larvae of Nerine cirratulus, differ greatly, as 
pointed out above (p. 615) from the larva of this species 
figured by Claparéde and Mecznikow; and as nototrochs 
occur on every segment after the 2nd, and gastrotrochs 
