F. J. Meggitt 
401 
its hooks being firmly fixed in the tissue and its extreme apex being 
buried in the villus. There is thus a certain strain upon the epithelium, 
but in the majority of cases this does not amount to much and does 
comparatively little damage. It is peculiar that while sections show 
the hooks to be buried their whole length in tissue and the rostellum 
thus apparently inextricably bound to the villus, yet an exposure of 
five minutes to the air, or a short dip in water or salt solution, produces 
its complete freedom. 
The whole strobila in its natural state appears to shelter as much 
as possible among the villi, possibly with the object of avoiding as far 
as possible being swept away with the food. 
In some respects Amoebotaenia sphenoides occupies an intermediate 
position between Davainea cesticillus and D. dubius. In the former, 
attachment depends entirely upon the rostellum, the suckers taking 
no part: in the latter, the suckers take a prominent part, the rostellum 
appearing to have comparatively little function. In Amoebotaenia 
sphenoides on the other hand, the rostellum still retains its function of 
fixation, being aided by the powerful development of the suckers. 
It is possible that the powerful acetabular armature of hooks in D. dubius 
explains the paramount importance of the suckers of that species. 
The behaviour of the rostellum differs in the two species of Davainea 
and in Amoebotaenia. In D. cesticillus and in the few cases of D. dubius 
where the rostellum is functional, its hooks are always inserted into the 
intestinal tissue, and the rostellum then retracted as far as possible into 
the head. In Amoebotaenia on the other hand, the hooks are far more 
deeply inserted, but the rostellum is fully extended longitudinally and 
contracted transversely as much as possible, the proper insertion of the 
hooks apparently depending upon the drag caused by the weight of 
the body and the action of the suckers. 
From the point of view of damage to the intestine, Amoebotaenia, 
owing to its smaller size and less powerful armament, is less dangerous 
than either of the two species of Davainea above-mentioned. The 
damage done is comparatively slight and is confined to a small amount 
of fragmentation of the duodenal tissue and an unavoidable loss of blood. 
It is only when present in extremely large quantities that this species 
would be able to cause much injury to the health of its host. 
Life-History. Since publishing the account of the anatomy of this 
species I have been able to obtain abundant material and consequently 
have been enabled to carry on infection experiments with a hypothetical 
intermediate host, the brandling ( Allolobophora foetida Eis.). The 
