618 FSH. IGRAVELY, 
and apparently always consisting of more than one row of 
cilia. Older larve bear only the posterior of these bands, and 
this in the later stages consists of a single row of powerful 
cilia like those of the characteristic bands of other Meso- 
troche. Whether this or the transitory anterior band corre- 
sponds to the anterior band of Fewkes’, Béraneck’s, and 
the Port Hrin larvee it is impossible to say, but as Wilson’s 
12-day larva is still unsegmented, and so corresponds to 
the monotrochal stage of Fewkes’ ? Phyllochetopterus 
larve and the Port Erin ? Chetopterus larve, I am 
inclined to think that its ciliated band is probably homo- 
logous with those of these larve, 1. e. that the posterior of 
the two bands described by Wilson corresponds to the 
anterior band described by these other authors. In the case 
of no mesotrochal larva other than those of Telepsavus 
costarum, Chetopterus variopedatus (pergamen- 
taceus) and Béraneck’s Chetopterus is the genus known 
with certainty ; but, as has just been shown, in at least two of 
these the line of separation between the first and second 
body-regions of the adult is indicated in the larva by a meso- 
troch, and in the third no evidence is at present forthcoming 
on this point. 
It is clear that no larval structures which are thus the out- 
come of the correlation between larval and adult structures 
can be regarded as independent positive evidence in favour 
of a classification itself founded upon these adult structures, 
whatever their practical systematic value may be. 
In the following account, therefore, special note will be 
taken of those characters which do not appear to show such 
dependence on adult structure, wherever any such can be 
found. Theextremely limited number of Polychet larvee 
which have as yet been described in any detail should be 
borne in mind, for it is of necessity only on this minute 
fraction of those which we know must exist that the following 
suggestions are based. 
The pelagic larvee of the Nereidiformia are characterised by 
the early development of the appendages in their ultimate 
