THE ANATOMY OF AMPHIPTYCHES URNA. 139 
system, such as exists in Trematoda. A nerve ring is present in Amphiptyches, but 
this is at the opposite end, and it is the presence of this which leads me to regard 
this end as the anterior. Certainly the reproductive organs open near the sucker end, 
but their structure and relationships are considerably different to that obtaining in 
the Trematoda, and can furnish no decisive evidence. They are apparently much 
more Closely allied to those of Caryophylleus than to those of the Trematoda or 
ordinary Cestodes. 
The opposite extremity of the body (posterior of Wagener) is very different in 
appearance, being characterised, as already. described by Wagener, by a rosette of 
folds. It is pierced in the centre by a small tubular space leading into the body, 
which space, after traversing a very short distance (not more than one eighth of an 
inch), turns dorsalwards and opens to the exterior through a slight proboscis-like 
structure on the dorsal surface. This proboscis is capable of extrusion and retraction. 
In the three specimens secured by myself it was retracted, but in one, for which I am 
indebted to the kindness of my friend, Dr. Haswell, of Sydney, it is extruded, and 
forms (PI. 1, figs. 2 and 3) a prominent feature close beneath the rosette of folds which 
marks the anterior end of the body. In this specimen also the sides of the body are 
much less crenate, which may perhaps be due to the fact that the food yelk glands 
are much less developed than in the three other specimens. When retracted the 
dorsal opening simply has the form of a short slit. This slit and the protruded 
proboscis have been figured already by Wagener (Pls. 14 and 15). It is difficult to 
assign any function to this curious structure, or to homologise it with anything 
present in other Cestodes, or in fact in other Vermes, but as will be shown later, the 
nerve cord has a definite relationship to the canal which pierces the anterior extremity 
and opens on the proboscis. Over the whole surface of the body spines are scattered, 
much as in certain Trematodes; the sharp pointed ends of these (Pl. 13, Fig. 6) 
protrude from the apex of a slight papilla, and in connection with each are special 
muscles which, on contraction, cause the spine to be protruded. These spines are 
irregularly distributed and are most numerous on the margins of the body and over 
the surface at the posterior and anterior extremities, as described by Wagener. 
The posterior end, as before said, is marked by the presence of a small opening 
leading into a sucker. Slightly more than half an inch beyond this, and on the left 
side ventrally, is present, in the dead worm, a well-marked somewhat conical and 
muscular papilla (Pl. 11, Figs. 1 and 4). The three worms obtaimed by myself were 
placed before killing between plates of glass, so as to prevent the contraction and 
curling up of the body when hardened, and in these three the papilla was but feebly 
marked, and the genital opening, which is placed at the apex (when the papilla is 
present), was almost upon the margin of the body. On the ventral side of the body 
also, and just at the base of the papilla towards the middle line, is another opening 
