t 
? 
LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 673 
continued for a month, during the first week of which I daily 
examined the viscera from one of each of the six species of 
experiment fish. During the last three weeks the examina- 
tions were made at intervals of a week. 
In a black bass (Centropristis striatus) which I killed 
on the fourth day I found ten Gasterostoma in an advanced 
stage of development. Later experiments convinced me that 
these were not a result of my feeding experiments. 
The failure of this feeding experiment gave me the choice 
of two alternatives : 
Ist. Hither the cercariz were not at such a stage of de- 
velopment that they were able to resist the action of the 
digestive juices of the intended host, or— 
2nd. The fish which I experimented upon were immune: 
toward this particular parasite, a conclusion which did not 
seem correct since one of the experiment fish contained Gas- 
terostoma, although, out of forty-six black bass examined 
during this and the preceding summer, I had found none 
which contained Gasterostoma. 
I felt justified, therefore, in concluding that the host of the 
adult form of Bucephalus was not necessarily an oyster-eating 
fish. 
In the meantime, as has been already noted, I had been 
attacking the problem from another direction. 
The Search for Gasterostomum. 
In 1902, while the first set of experiments was being 
carried on, I attempted to find the host of Gasterostomum, 
which the concensus of opinion of the various workers on 
Trematodes, based on the similarity in structure of Bucepha- 
lus and Gasterostomum, suggested as the probable adult 
form. 
This search was carried on rather blindly, and during that 
season resulted in nothing. Many fish were obtained by 
seining in the vicinity of the oyster-beds, but although they 
served as the hosts of innumerable parasites, Gasterostomum 
