LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 677 
show that they served in any way as temporary hosts for 
Bucephalus. 
It is quite possible that the Silverside obtains them during 
their free-swimming stage. A careful examination of many 
of the smailer fish (Dr. Linton has already found encapsuled 
forms in the anchovy [Stolephorus brownii]) will, I 
think, reveal the presence of larval Gasterostomum forms. 
That it is necessary for Gasterostomum to undergo a 
portion of its life-history within the Silverside or a small fish 
of similar habit I doubt greatly. 
Giard (80) found encysted stages of Bucephalus in 
Belone vulgaris, a gar fish. I can see no reason why the 
gar may not obtain some of its Gasterostoma first hand, i.e. 
that it may obtain cercariz during its feeding, the cercariz 
encysting within the gar’s body, as Giard has described, and, 
after reaching its adult sexual condition, breaking from its 
cyst to attach itself to the wall of the intestine of its host. 
The hypothesis proposed by Giard that Gasterostomum 
larve in Belone vulgaris probably reach their adult con- 
dition in some fish which preys upon this gar does not seem 
to me necessary. 
The Genus Gasterostomum. 
It would be preferable, for several reasons, if the matter 
of the present section were placed at the end of the historical 
account of Gasterostomum; but inasmuch as it has its founda- 
tion in the observations and experiments detailed in the 
present paper, it seems better that it should follow the 
account of these experiments. 
After studying the form which is the subject of this paper, 
and seeing the many changes of appearance which it is 
possible for a single specimen to assume, considerable doubt 
arises in my mind as to the genuineness of the many species 
which have been described. 
Wagener’s (3) beautiful figures of young G. fimbriatum 
vou. 49, PART 4,.—NEW SERIES. 49 
