Mons. Giard is of opinion that the singular larvæ known as _Bucephali_ attain sexual maturity in sharks and dog-fishes; therefore it is extremely unlikely that the _Bucephali_ should have been in any way concerned in the infection of our missionary and his wife; nevertheless there remains the probability that these human bearers swallowed other kinds of Trematode larvæ when they consumed the Ningpo oysters. Moreover, if it should happen that none of the other larvæ occurring in oysters are capable of developing into flukes in the human territory, it yet remains highly probable that some one or other of the various encysted (and therefore sexually immature) Trematodes known to infest marine fishes will turn out to be the representative of our _Distoma crassum_. In this connection we must not forget that the flesh of the _Salmonidæ_ forms the probable source of human _Bothriocephali_; and there is some likelihood that salt-water fishes, if not actually the primary, may become (after the manner explained by M. Giard) the secondary intermediary bearers of fluke-larvæ. At all events, I am inclined to look to the Ningpo oysters, or to some other of the various species of marine shell-fish sold in eastern markets, as the direct source of _Distoma crassum_; for, in addition to the bucephaloid cercarians, we have abundant evidence of the existence of other and more highly developed fluke-larvæ in marine bivalve mollusks. In this connection I will only further observe that we possess very little knowledge of the parasites which take up their abode in the viscera of savages. This ignorance results partly from the fact that these untutored races, as proved by the statements of Kaschin and others, actually, in the matter of severe symptoms, suffer much less from the presence of intestinal worms than their civilised fellow-men do. The subject is worthy of further attention, but no one, so far as I am aware, has cared to institute the necessary inquiries in a methodical way. I strongly suspect that several of the human parasites which we now consider to be rare would be found to be abundant if by means of post-mortem examinations and other methods of investigation we could be made acquainted with the facts of helminthism as they occur amongst the raw-flesh and fish-eating savage tribes. Of course any person, notwithstanding the utmost care and cleanliness, as in the cases before us, may contract a noxious parasite; nevertheless, speaking generally, it may be said that the measure of internal parasitism affecting any given class of people bears a strict relation to the degree of barbarism shown by such persons in their choice of food and drink, and in their manner of eating and drinking. This statement, if true, is not destitute of sanitary importance; moreover, it applies not alone to ourselves, but also to all the domesticated animals that serve our wants. Cleanliness is just as necessary for their welfare as for our own.