AND ANOTHER ALLIED ORGANISM. 57 



true. If a sporocyst, it is an anomalous one, and furnishes a 

 subject for good work in tracing its parentage. 



DESCRIPTION OF PLATE HI. 



Fig. 1. — A nurse of Cercaria ephemera provided with a prolonged digestive 

 canal, a, moutli cavity ; b, intestinal canal ; c, a Cercaria ephemera 

 already developed in its interior ; d, germinative bodies which have not 

 yet become Cercariw. After Siebold. This nurse is found living on 

 Planorbis corneus. 



Fig. 2. — A portion of the structure in which Bucephalus Haimeanus is found, 

 magnified about 12 diameters, a, is a blind extremity — these are 

 abundant in certain stages ; b is a peculiar looking nodular termination, 

 perhaps caused by the everted edges of a ruptured portion, a different 

 example of which may be seen at c. 



Fig 3. — A diagrammatic representation of what looks like the attachment of 

 egg sacs to tbe structure containing Bucephahis Haimeanus. A portion 

 thus teazed out in water, when examined with a high power, exhibits, 

 I think, an anatomical connection between the egg sacs and the tubular 

 structure. Tbe appearance, however, may be caused by the presence 

 of the structure in the genital ducts. 



Fig. 4. — Cercaria ephemera, after Siebold; it is half the size of his drawing. 

 a, mouth cavity ; b, intestinal canal ; c, d, urinary organ ; e, queue ; 

 /, three spots of pigment. 



Fig. 5. — Bucephalus Haimeanus. a, mouth ; b, lamellar appendages; c, pad ; 

 d, central organ. 



Fig. 6. — Bucephalus, from Mytilus edulis. a, mouth ; b, lamellar appendages 

 c, pad ; d, central organ. 



Fig. 7. — Stages of development of Bucephalus Haimeanus. 



Fig. 8. — Stages of development of Bucephalus from My tilts. 



Fig. 9. — Granular masses found in abundance in the tubular structure in which 

 Bucephalus Haimeanus. and the other Bucephalus is found. 



Fig. 10. — Diagrammatic figure showing the appearance of the central organ 

 when viewed in the long axis of the body. 



Fig. 11. — Diagram of the pad of the Bucephalus from Mytilis edulis. 



Fig. 12. — Cercaria ephemera encysted ; after Siebold. In the three figures from 

 Siebold I have merely given the outline. 



