1909. | TAPE-WORMS OF THE RED GROUSE. 353 
and but for the prominent posterior lip the segments would be 
square. The posterior segments are, however, longer than they 
are broad, and quite at the hinder end they are attached to one 
another by but a slender connection. The prominent posterior 
angle is maintained to the last. It is, however, difficult to give 
precise statements as to the condition of this worm. In some, one 
region of the body will be swollen out; in other specimens, other 
yegions will expand. Some have a ‘thin, papery consistence ; 
others are plump and almost circular in section. Sometimes 
the posterior rim overlaps the anterior region of the succeeding 
segment, so that the whole resembles the pile of conical caps which 
clowns used—TI do not know whether they still do so—to wear in 
the circus. These varying conditions doubtless depend largely 
on the state of the parasite when killed and on the means taken 
to kill them. The genital pore is, except in rare cases, on one 
and the same side. 
The anterior end tapers quickly to the very small, squarish head 
(Pls. LVI. & LIX. figs.2&6). Anteriorly, the head ends in a ros- 
tellum, which seems nearly always to be retracted into a shallow 
recess. At each of its four corners the head bears a large sucker, 
as a rule circular, but at times oval in shape, and then the long 
axis is longitudinal. 
Both rostellum and suckers bear hooks, which differ, however, 
both in their arrangement and shape. The hooks of the rostellum 
are arranged in a double row, Each is shaped something between 
a Y and a T (PI. LIX. figs. 7 & 8), one arm being more curved 
than the other and it is this arm which is anterior. The stalk 
of the hook is but very slightly curved, and the posterior row 
alternates with the anterior. The length of the hooks is between 
6-9 « and 66. The shape of the hooks does not vary appreciably 
and the arrangement in two rings is very regular. ‘These hooks 
were not seen “by Baird and were first recognised i fi LEO A, 
The hooks on the suckers are also very ‘minute, and they vary 
considerably in size: the largest forms are about as long as the 
vostellay hooks, 7. ¢. 6°6 p; the smallest forms are perhaps half 
this size, and Mena are intermediate sizes. Each hook is slightly 
curved and tapers to a fine point, each possesses a “ heel” which, 
as is shown in fig. 10, Pl. LIX., is developed in varying degrees. 
In many cases tne proximal end resembles the “head” of a 
thigh-bone. The hooks are arranged in a ring, but the ring 
contains no definite and regularly arranged rows, rather it is a 
small circular forest or hedge of hooks of varying sizes and shapes 
(Pl. LIX. fig. 9). 
The head is usually followed by an unsegmented neck, three or 
four millimetres in length, but I have seen one or two specimens 
in which the segmentation occurs immediately behind the head. 
In transparent specimens longitudinal muscles running to the 
suckers can be seen traversing the neck. «In most specimens the 
* F.S. Monticelli, Boll. Soc. Napoli, ser. I. v. 1891, p. 155, 
