272 
Life-history of Moniezia 
scopically. Result, negative. Shortly before this, as already noted, Dr Lebour 
had conducted experiments on feeding proglottids to various slugs and snails 
but had not been able to get the eggs to develop. My own conviction is that 
in spite of their appetite for tapeworm proglottids (see Lebour, 1915 and Grassi 
and Rovelli, 1892), they are very unlikely hosts for the parasite since in the last 
resort the lamb would require to swallow them, and this, for the reason we 
have seen above, it would be very unlikely to do. On the other hand, of course, 
it is always possible that, as noted by Miss Lebour, the eggs may undergo 
some alteration during their passage through the slug’s intestine which, though 
not apparent, may influence their development in other ways. Slugs are not, 
however, by any means the only animals capable of rendering such a service 
to the tapeworm. For instance, my colleague Mr C. L. Walton and myself 
once derived considerable amusement from watching hens busily engaged in 
swallowing tapeworms lying on the floor of the Aberystwyth slaughter-house. 
In thinking over the various invertebrate animals capable of acting as an 
intermediate host, one cannot avoid being struck by the fact that while, as 
was already remarked, the variety of invertebrate life visible on a pasture 
at lambing time is very small yet one class of animals at least is exceedingly 
well represented, even at that early period in the year. These are the many 
coprophagous forms which live in sheep and cattle dung, especially Aphodius 
spp., small Staphylinids (Aleocharis) and mites. I have repeatedly seen species 
of Aphodius feeding in sheep dung which contained tapeworm proglottids and 
it seems inevitable that they should ingest tapeworm ova. It was not till 
some years later, however, that I was able to explore this possibility further 
and my conclusions concerning it are given later in this paper. 
The remainder of a short research period in Aberystwyth was devoted to 
testing the possibility of the lamb becoming infected directly from the mother 
ewe, while sucking. In view of the early age at which lambs are infected it 
seemed not unreasonable to make the following hypothesis. Sheep when 
feeding ingest the ova which lie about the pasture. These ova then develop 
into hexacanth embryos which, in the case of the ewes, make their way, or 
eventually get carried, to the region of the udder. There they may develop 
into larval forms and remain till the ewe drops her lambs when they 
are passed to the lambs w T hile sucking. The feeding process is a very energetic 
one on the part of the lamb and might well provide the stimulus necessary 
to liberate the larval Moniezia from the tissues in which it is lying into an 
adjacent milk duct and thence into the teats. There is nothing to prevent such 
a course of events provided the larva is of minute size, which it may quite 
well be. We may note, for instance, that Curtice and, later, Hassall, found 
numbers of very young forms of an unarmed tapeworm—probably Cittotaenia 
variabilis —in rabbits, which were less than 1 mm. in length, one being as small 
as 0-304 mm. 
Obviously, the experimental work required to test such an hypothesis 
ah initio would need to be of a very careful kind. A short cut would be effected 
