291 DE. T. S. COBBOLD ON THE LAEGE HUMAN FLUKE. 



differ materially from those obtained by Lacaze-Duthiers from 

 the Mediterranean. 



Prom all the facts at present before us M. Griard argues tliat 

 it is most probable the Bucephali of the garfishes attain sexual 

 maturity as Gasterostomata in sharks and dogfishes, and perhaps 

 also in certain large species of Gadidce, which feed on the gar- 

 fishes when they frequent the shore for the purpose of spawning. 

 In drawing this conclusion, M. Griard has probably been much in- 

 fluenced by the opinion of Von Siebold, who long ago suggested, but 

 of course could afi"ordno experimental proof, that Bucephalus poly - 

 morphus was the larval representative of Gasterostoma fimhriatum. 



If we accept these views, as I believe we must, it becomes ex- 

 tremely unlikely that the Bucephali should in any way be con - 

 eerned in causing the infection of our missionary and his wife ; 

 nevertheless there remains the probability that the human bearers 

 in question swallowed other kinds of Trematode larvae when they 

 consumed the Ningpo oysters. Moreover, if it should happen 

 that none of the other larvae 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 Di- 

 stoma crassum. In this connexion we must not forget that Leuck- 

 art has pointed to the flesh of Salmonidse as 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-larvse. 



On the whole, I am still 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 evi- 

 dence of the existence of other andj more highly developed fluke- 

 larvae in bivalve moUusks. So far back as the year 1841 Mr. 

 Garner, F.L.S., in his paper on the Lamellibranchiate Conchifera 

 (Zool. Trans, vol. ii.) referred to a species of Bisfoma in the 

 freshwater Mussel ; and he subsequently attempted to prove the 

 parasitic origin of pearls from a similar source (Brit. Assoc. Eep. 

 1862). I had an opportunity of examining some of these Bisto- 

 mata, and satisfied myself that they were only sexually immature 

 forms awaiting their final passive transference to the intestine of 



