Davaineid Cestode from a Wallaby. 605 
the usual Davainea type (fig. 2 a), and are set in two rows, 
the hooks of the posterior row irregularly alternating with 
those of the anterior row. ‘They are all of the same size, 
measuring about 9 long. The crown formed by these 
hooks is very striking, in that they bound an area resembling 
that of an equal-armed cross, the extremity of each of whose 
arms is bifid. Hach ray with its subdivisions occupies the 
middle area of one of the lobes of the protuberance, the four 
rays meeting on the anterior face of the protuberance. 
These hooks easily become detached, and consequently it 
was not possible to determine their number, but a rough 
estimation placed them at about 650 for each row. 
The rest of the head, which is slightly broader than its 
anterior protuberance, is separated off from it by a well- 
defined constriction. 
There are four rounded suckers placed on slight elevations, 
each elevation being situated opposite one of the depressions 
in the anterior head protuberance; thus they occupy a 
somewhat lateral position, two being subdorsal and two 
subventral. The outer margin of each sucker is beset with 
numerous small hooklets, about 5 w long (fig. 2 6), arranged 
in diagonal rows of about a dozen hooks in each row, ‘I'he 
suckers are somewhat cup-shaped, measuring about 130 u 
across their mouths and having a depth of about 70 p. 
(c) Neck.—A distinct neck is present, which is of a 
uniform breadth throughout its length. Its breadth, in 
different worms, varies from 380 4 to 417 yw, and its length 
varies from 800 to 1200. ‘This variation appears to be 
due to the different sizes of the worms, and also to different 
states of contraction. 
(d) Segments.—The first-formed segments are very short, 
and are as broad as the neck, the older segments increase 
both in length and in breadth, until about the middle of the 
strobila is reached, where they are about 230 long and 
4mm. broad. As the segments become ripe they increase 
in length and decrease in breadth, so that the ripe segments 
at the end of the body are about twice as long as broad, 
measuring about 2°5 mm. in length by 1°3 mm. in breadth. 
INTERNAL ANATOMY, 
(a) Muscular System (fig. 3)—The longitudinal muscle- 
system is well developed, and consists of a single layer of 
irregularly scattered muscle-fibres occupying the dorsal and 
ventral thirds of the proglottid. The transverse muscle- 
fibres form a thin layer of delicate fibres immediately 
internal to the longitudinal muscle-fibres ; they bound the 
