EEPOET ON THE ANNELLDA. 
31 
Instead of the preoral folds the minute head of the animal forms the anterior border 
of the snout. In shape it is somewhat ovoid or occasionally lozenge-shaped, from the 
pointed nature of the anterior edge. It bears on the dorsal surface four eyes, all nearly 
equal in size, and forming a rectangle, those of each pair being close together, thus 
diverging from the ordinary type in the Amphinomidse. Somewhat behind the posterior 
pair of eyes is the long median tentacle, a simple subulate process which projects 
backward as far as the middle of the second body-segment. A little in front of the eyes 
at each side is a tentacular cirrus, considerably shorter than the foregoing ; while 
on either side of the tip of the snout is another of similar length. The mouth 
opens on the under surface at the anterior border of the second body-segment, and a flat 
surface, marked by two narrow longitudinal ridges, leads forward to the tip of the snout. 
The posterior end terminates in a bulbous anus, which in some appears pediculated, from 
the constriction immediately in front. 
The branchiae commence on the fourth body-segment as a considerable tuft in each 
case, and when fully developed consist of a slightly divided arbuscle richly coated with 
cilia, and thus diverging from the condition in the Amphinomidae. Moreover, the hypo- 
derm of the organ presents a lax and cellular appearance, while the cuticle is very thin on 
the distal processes. In transverse section the translucent areolar hypoderm is especially 
marked at the base of the organ. The central area is occupied by large granular globules, 
apparently coagulated blood, and the latter also occurs in the two channels in the distal 
branches, v/hich are irregularly dichotomous. The cilia appear to form several rows on 
the sides of the processes. The branchiae in the Hippoyioe cranchii of Baird are decidedly 
larger. 
The dorsal bristles form a broad fan-like tuft at the anterior border of each segment, 
extending from the dorsal to the ventral aspect of the foot, and with the slight concavity 
of the curve directed backward. The bristles are translucent, simple, and tapering 
(PI. IIIa. fig. 13). The outline of the lower part of the shaft (PI. IIIa. fig. 16) is slightly 
irregular, from indications of the points or spikes, which become more distinct distally, 
and there is a single median streak probably due to a ridge externally, the rest of the 
surface being marked by fine longitudinal lines. In the figure the shaft is comj)ressed 
and cracked, but the spikes are thus rendered more evident. In its normal condition the 
lower part of the shaft appears as a clear tubular bristle (PL IIIa. fig. 15), only a slight 
roughness along one of the margins indicating the spikes. The mere evaporation of a 
small portion of the water between the cover and the slide suffices to destroy the outline 
by breaking the tube and causing it to resemble fig. 16 . The tips of some are peculiarly 
bifid (PI. IIIa. fig. 14). Acetic acid has very little effect on these bristles except in 
rendering them more translucent. No bubbles of gas escape, and they are less brittle 
than in the Amphinomidse ; so that on the whole they do not seem to be of the same 
characteristic calcareous nature. 
