193 
crotchets, the smaller number being present in the iirst 
three or four neuropodia. In the branchiate Lytham 
specimen 39 mm. long, the crotchets are rather move 
numerous, there being eight or nine in many of the 
neuropodia. The crotchets of post-larval stages differ 
from those of adults in the relatively large size of the 
teeth, and im the angle which the rostrum makes with 
the shaft. In post-larval crotchets the rostrum is approxi- 
mately at right angles to the shaft, while in older speci- 
mens it makes a much greater angle, in large specimens 
as much as 130 degrees (cf. figs. 15, 18). 
As stated above, there are no gills in any of the seventeen 
post-larval stages examined, except one. This one is 
+9 mm. long, and the thirteen pairs of gills are present, 
and all except the first two are branched. The largest 
gills are behind the middle of the series, and this is pro- 
bably the region where the gills are first formed. = In 
other specimens no gills are indicated, but im the living 
specimen 46 mm. long, unmediately behind the notopodia 
of the penultimate and the two or three preceding chieti- 
gerous segments, the blood-vessels form a well-marked 
loop, as if preparatory to the formation of a gill, and there 
is a very slight elevation of the skin in this region. Later 
on, as shown in the Lytham specimen, the gill becomes 
successively a papilla, a digitiform, and then a branched 
structure. The gill arises, therefore, as a special respira- 
tory structure, and is not a dorsal cirrus which secondarily 
becomes a branchia. 
The tail is very similar to that of the adult. The 
terminal segment bears a number of circum-anal papille, 
each of which carries a tuft of four or five sense-hairs, 
which project posteriorly. 
The skin is glandular. It contains numerous 
scattered cells, each filled with yellow granules, If the 
O 
