Abstract
Various investigators (Muto, 1 2 Faust and Khaw, 3 Yamaguti 4 ) have in the past described the cercaria of Clonorchis sinensis but none of these investigators have given complete experimental proof for their statements. Such proof would seem all the more necessary because these different descriptions did not, on the whole, agree well with each other. Correct knowledge of the cercaria of C. sinensis is of special value because with such knowledge it is possible to examine and discover which snail acts as first intermediate host of this parasite.
In order to obtain the cercaria which, beyond question, is that of C. sinensis, it is obviously necessary to infect snails with Clonorchis eggs and to achieve a full development to the cercaria stage in these snails. Although several investigators (Nagano, 5 Faust and Khaw) realized the importance of this fact, their attempts were unsuccessful so far as complete experimental proof was concerned.
Instead of using old snails collected from rivers and ponds as has been done by former investigators, the present writers used laboratory-bred young snails which may be regarded as not only free from a previous infection with larval stages of trematodes but also as being much more easily infected than older snails. The following is the report of a successful experiment concerning the development of C. sinensis eggs to the cercaria stage in laboratory-bred young snails, Bithynia fuchsiana.
In the first part of April, 1938, a large number of B. fuchsiana were collected in the vicinity of Peiping and kept in an aerated aquarium. Within a few days, eggs of this species of snails were laid on the glass wall of the aquarium and were immediately removed to another aquarium.
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