LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 641 
Historica Account or BUCEPHALUS. 
Several varieties of Bucephalus, the larval form of species 
of Gasterostoma, are known. 
B. polymorphus, von Baer (18, 1827), from Anodonta 
mutabilis, var. Anatina and Cellensis, and from Unio 
pictorum. 
B. intermedius, Ulicny (19, 1878), from Anodonta 
cellensis. 
B. haimeanus, Lacaze-Duthiers (20, 1854), from Ostrea 
edulis and Cardium rusticum. 
B. crux, Levinsen (16, 1881) from Modiolaria discors. 
B. cuculus, McCrady (21, 1874), from oysters at 
Charleston, South Carolina. 
Cercaria bucephalus, Ercolani (22, 1880), from Unio 
and Anodonta. 
Bucephalus von Baer, Haswell (23, 1903), from Mytilus 
latus. 
Baer (18) describes and figures the thread-like germ-tubes 
and the cercariz as they appeared under low magnification. 
He thinks it probable that the germ-tubes were propagated 
by sprouting (“Sprossen”’) and also through the develop- 
ment of young tubes from the tails of the cercariz. 
Siebold (1) recognises that the gut is simple, and sees that 
the mouth opening is upon the middle of the ventral side of 
the body. He is of the opinion that Bucephalus is related to 
Gasterostomum. 
Wagener (24, 1858), from the anatomical resemblance, 
thinks it probable that B. polymorphus becomes G. fim- 
briatum. Healso describes (8, 1857) a bladder-like struc- 
ture ‘01 mm. long from which are given off two slender tubes, 
which, both together, are one fifth of a mm. long. The 
bladder contained cells; the tubes were empty. This 
structure, I take it, may have been a rather young sporocyst. 
Pagenstecher (25, 1857, and 26, 1863) found Bucephalus in 
Anodonta anatina. He describes and figures the animal 
