30 MR. W. K. HUTTON ON THE [Jan. 20, 
length, and containing within it the more important organs, comes 
fa airly stout and muscular portion 2 mm. in diameter (Plate VI. 
fig. 1, A). This gradually passes posteriorly into a much slighter, 
less muscular, and longer part, which extends for more than the 
middle third of the length and measures 1 mm. in thickness ; 
while lastly, there is a short, thick, ellipsoidal piece, measuring 
5 mm. by 2°5 mm., having very thin walls which are transparent 
enough to allow the coils of gut within to be dimly seen. This 
terminal portion is quite sharply demarcated from the rest of the 
body, and forms a sack in which the coiled portion of the intestine 
(Plate VI. fig. 2, G) is contained. 
The colour of the spirit-specimens is a pale yellow over the 
anterior three-fourths of the animal’s length; on the thick 
terminal part the tint is a dirty bluish white, the contents of the 
intestine appearing through the body-wall as brownish markings. 
The skin has a slightly iridescent sheen; it is entirely devoid 
of papille and is of a leathery toughness. It is studded with the 
openings of innumerable cuticular glands (Plate VII. fig. 6, C.G.). 
These glands (Plate VI. fig. 3) are spheroidal, and measure ‘05 mm. 
in diameter. Each is lined with a single layer of rather flattened 
cells (LL), and the majority are completely filled with small yellow, 
highly refractive granules (I). The glands on the introvert are 
very much smaller, and granules are not so plentiful in them as 
elsewhere. 
Though definite papille are not found, tegumentary appendages 
are represented on the introvert by chitinous hooks. These are 
arranged in a series of ten transverse rows (Plate VI. fig. 4). 
The individual hooks vary in length (Plate VIT. fig. 5) from -06 
to:08 mm.; they are brown in colour, almost black at the tip, are 
but slightly curved, and the isolated hooks shown in the figure 
are grooved on their concave edge for about two-thirds of their 
length (Plate VII. fig. 5, F). Each hook has a small multicellular 
epidermal core. The first part of the introvert, that nearest the 
“head” of the animal, is perfectly smooth, and, when invaginated, 
abuts against the outer surface of the tentacular crown through- 
out two-thirds of its length; for the remaining distance, however, 
the tentacles touch the hook-bearing part. Laceration of the 
tentacles during evagination and invagination is averted in some 
Sipunculids by the presence of a “collar,” which intervenes 
between these delicate structures and the rough introvert. Here 
there is no such Jprovision; the end is gained by a transverse 
furrowing of the skin on the hook-bearing introvert during 
invagination ; and by this means the hooks, projecting from the 
base of the groove, barely come into contact with the tentacles. 
An indication of this condition is represented in fig. 6, H.I. 
(Plate VII.). 
General Arrangement of Organs. 
Figure 2 (Plate VI.) is a drawing of a dissection of the worm. 
It has been opened along the ventral aspect, and the two retractor 
