F. J. Meggitt 
265 
groove in the posterior extremity of the preceding one, the proglottides 
thus fitting telescopically into one another. Cuticle and sub-cuticula 
are absent from the groove and from the anterior margin, so that the 
parenchyma of one segment is in direct communication with that of 
another. This can easily be seen in mature proglottides, when the ripe 
eggs from one may intrude into a neighbouring one : as a rule, in the 
posterior part of the strobilus, there is no internal separation whatever. 
A younger detached proglottis shows anteriorly and posteriorly a distinct 
parenchymatous boundary. 
The following table gives the external measurements according to 
various workers. It can be easily seen that there are discrepancies, 
though these might be expected. The active nrovements of the worm so 
alter its size and shape that it is impossible to measure accurately a 
live specimen : measurements thus obtained may double or halve 
themselves according to the state of expansion or contraction at the 
time. In a similar manner, measurements, especiallv of the head, of 
dead specimens are unreliable owing to the varying shapes assumed by 
the worm when dying, and the conserpaent apparent alteration in size. 
The figures given below are only approximately correct, those occurring 
most frequently in a large number of measurements having been taken as 
normal. It is apparent that sizes exceeding these have been obtained, 
and that these extremes cover and thus neutralise the discrepancies 
before mentioned. 
Length Breadth Thickness Length of Breadth of 
® head of head of head rostellum rostellum 
von Linstow 
2 
— 
— 
Magelhaes .. 
3-4 
0-2 
0-205 
Cohn 
2-75 
0-14 
0-2 
Meggitt 
2-5 
0-213 
0-162 
0-220 
Length of 
hooks 
0032 
— 0T5 0-0375 0025 
— 0T5 0-037 0-025 
0-098 0-167 0-039 0-026 
von Linstow 
Magelhaes 
Cohn 
Meggitt 
Size of suckers 
0-075 
0-11 
0-1218 
0-0784 
Size of egg 
0-042 
0-028 
0-0294 
All measurements in mm. 
Rostellum. 
The head is provided with four suckers and a well-developed apical 
rostellum. 
The rostellum (PL XX, figs. 5 and 6) consists of two parts, a muscular 
protrusable axis (a), and an ensheathing case (c.r.). The latter is 
Parasitology vii 
18 
