A Study of the Life-history of Bucephalus Haimeanus; a Parasite of the Oyster

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Abstract
The observations detailed in this paper maybe summarised as follows: 1. Germ-cells which arise within the wall of the sporocyst of G. gracilescens give off small cells, which may be considered of the nature of polar bodies, segment, and develop to the cercaria B. haimeanus. 2. The cercaria B. haimeanus, Lacaze-Duthiers (1854) = B. cuculus, McCrady (1868), parasitic in the oyster, differs structurally from B. poly tnorphus, von Baer, parasitic in fresh water mussels, only in the shape of the tails. 3. G. gracilescens, Wagener (1852) parasitic in Lophius piscatorius = Gasterostomum sp., Linton, 1899, parasitic in Tylosurus mar in us, differs from G. fimbriatum, von Siebold, only in habitat (one is a marine, the other a, freshwater, form), and slightly dissimilar larva. 4. B. haimeanus, as shown by experimental evidence, is a larval stage of G. gracilescens. 5. Experimental evidence shows that supposedly different species are physiological varieties of the same species. 6. The presence of the sporocysts and cercaria of G. gracilescens in the oyster prevents the formation of reproductive elements, and also renders the host incapable of withstanding adverse conditions. 7. B. haimeanus thrives best in oysters growing in brackish water. Its growth is inhibited by increased salinity. It will be noticed that there is one gap in my account of the life-history of Gasterostomum. I have not yet proved the infection of oysters by embryos developed from the eggs of the adult. I hope to make this the object of experimental work within the near future.

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