404 SPIRORBIS GRANULATUS. 
furnished with granular glands, for a gizzard-like portion is marked off by constrictions in 
front of it. It is ciliated from this region to the vent, and elongated collections of particles 
are often observed in motion in the interior of the gut. Gregarines are common in the 
intestine, and they are active, contracting and elongating the anterior end, which is now 
bulbous and again pointed, and bending their bodies to and fro. They are much more active 
than the Gregarines of Nemerteans, the contractions and elongations of the entire body 
and the tapering of both ends being noteworthy. The myophan striation is most marked 
in contraction. The body is minutely granular, and the large nucleus is about the centre. 
In the ccelomic space numerous minute ovoid bodies—tapered at one end—also occurred, 
and they had a tendency to group themselves in circular masses. These represent the male 
elements. 
Two brownish-green granular glands (Plate CX XII, fig. 7a, a) lie obliquely on each side 
of the gizzard-like region of the alimentary canal, and they open by a dorsal pore at their 
junction. 
The first, or collar-bristles, differ from those which succeed not only in size, but in direc- 
tion and structure. Hach (Plate CXXXII, fig. 5, and Plate CXXXVII, fig. 22) consists of 
a long straight shaft, slightly dilated and flattened as it approaches the tip, which is curved 
backward, and with fine serrations at its rounded base, their size, however, increasing as the 
gap 1s approached, three or four being especially prominent next the notch, then the blade is 
finely serrated to the delicately tapered extremity. Amongst these are a shorter series of 
more slender bristles with simple tapering tips. This bristle-tuft is directed forward nearly 
in a line with the long axis of the body, and the bristles are longer and stronger than those 
which follow. Moreover, as had been suspected, the boldly serrated region at the base of 
the tip is double—a modification of the ordinary wing. In an example from St. Andrews, in 
which the collar-bristles had apparently been broken, the terminal blade was finely tapered and 
translucent without evident trace of serrations, whilst the basal webs were coarsely spinose. 
In a very young specimen barely visible to the naked eye the collar bristles appeared to 
have no gap in the basal web. The two tufts of bristles which succeed are simple, with 
slightly curved spear-shaped tips (Plate CX XXII, fig. 5a), the last pair having the tips of the 
bristles somewhat broader. The second tuft has several bristles with sickle-shaped tips, the 
concave edge being characteristically serrated—that is, nearly at right angles to the axis of 
the tip. 
The posterior bristles are placed in pairs on each edge of the segments of the region, 
and in outline they somewhat resemble an ancient long-toed boot with the sole (edge) 
serrated. They diminish in size from before backward. 
The anterior hooks (Plate CX XXVIII, figs. 15 and 15a) have a long and minutely serrate 
anterior edge, but the main fang inferiorly is short in lateral view, and when looked at on 
edge is flattened and bifid. Whilst the dorsal outline slopes downward to the posterior 
border, the ventral edge, slightly incurving behind the main fang, is nearly horizontal. It is 
difficult to make out the exact nature of the posterior outline from their flexibility and the 
manner in which they adhere to each other. The teeth on the anterior edge are downwardly 
directed, long and sharp. The posterior hooks do not differ in structure, but are smaller. 
The greenish circulatory fluid is carried forward by a dorsal vessel, which is often curved 
in each segment, over the alimentary canal, and backward by a ventral trunk. 
