100 
ination of the species of Gracilaria which 
I have had under observation. 
In order to make the structure of the 
trophi and the arrangement of their chit- 
inous supports more clear, I have prepared 
fig. 2-4, to accompany the following de- 
scription. 
The head of the early form (fig. 2) is 
.much flattened. It has, upon its dorsal 
surface, two stout chitinous supports, which 
pass anteriorly toa point above the labrum, 
where they nearly meet, then turning lat- 
Fic. 2.— Ventral view of the head of Graci- 
laria syringella in its early larval stages: 0, la- 
brum; , mandible; 7, maxilla; p, antenna; a, 
b, d, e, f, 9, h, i, m, chitinous supports explained 
in the text; g, depression between the basal sup- 
port of the maxilla and the ventral surface of the 
head. 
erally and ventrally, at nearly right angles 
to their previous direction, they join with 
other chitinous supports to form the sockets 
of the mandibular joints. Posteriorly these 
two dorsal supports (the anterior portions 
of which are not seen in fig. 2) approxi- 
mate slightly and are connected by a trans- 
verse support (fig. 2, e) ; rapidly diverging 
again they join the ring which passes 
around the posterior portion of the head 
(fig. 2, f, m, g). From the lateral por- 
PSYCHE. 
tions of this ring there passes forward, on 
each side, a support (fig. 2, @), which turns 
suddenly inward and ventrally behind the 
antenna (fig. 2, p), and helps to form the 
socket of the joint of the mandible. About 
half way between the lateral supports (fig. 
2, a) and the middle of the ventral portion 
of the head, on each side, there passes for- 
ward from the ring which surrounds the 
posterior portion of the head another sup- 
port (fig. 2, b), which also helps to form 
the socket of the mandibular joint. From 
the points where the last-mentioned sup- 
ports join the posterior ring, supports (fig. 
2, d) pass anteriorly and obliquely toward 
the dorsal side of the head, joming the dor- 
sal supports about midway between e and 
the labrum. 
The labrum of the early form (fig. 2, 0) 
is supported beneath the d'verzent anterior 
extremities of the dorsal chitinous supports 
of the head in such a manner as to be ca- 
pable, not only of some protrusion and re- 
traction, but also of a slight lateral motion. 
The labrum is bilobed, each lobe bearing 
five incurved spines, and has a very delicate 
grooving (fig. 3, 0). 
The mandibles of the early form (fig. 2 
and 3,7) are strongly chitinized. They 
are of a generally triangular form, strongly 
rounded on the outer side and toothed on 
the inner side. Two prominent apical 
teeth are followed by a number of smaller 
ones. On the under-side of each mandi- 
ble, near the middle of the proximal end, 
is a rounded protuberance, which fits into 
a socket formed by the union of the sup- 
ports a and 6b with the laterally divergent 
anterior portions of the dorsal supports of 
the head, thus forming the mandibular 
joint. The pinniform extensor muscles of 
