SEA-FISHERIES LABORATORY. 105 



its floor, and the muscle fibres are much less prominent 

 along the median part of the basal wall than elsewhere. 

 These characters suggest that the bothridium really 

 consists of two structures, the adjacent walls of whicli 

 have fused together. It lies entirely below the general 

 surface of the scolex. Its posterior wall is entire, but 

 anteriorly the lateral walls thin out and disappear. The 

 proboscides, four in number, are situated at the anterior 

 extremity of the scolex. They are very short, almost 

 globular in form, and closely covered with short recurved 

 hooks. The dorsal and ventral pairs are in contact with 

 each other, but a little distance separates the two pairs. 

 Each proboscis is in relation to a sheath, into which it 

 may presumably be invaginated, though this did not 

 occur while I had the worms under observation. The 

 proboscis sheaths pass into muscular bulbs. All this 

 proboscidial apparatus resembles in every detail that of a 

 typical Tetrarhynchid, from which the scolex of 

 Coenomorphus differs only in the characters of the 

 bothridia. 



Muscles of the ScoJex. These differ in some respects 

 from those of the Tetrarhynchids. Lonnberg does not 

 give figures of their arrangement, so I have prepared 

 the diagram (Text-fig. 1). The muscle bundles originate 

 either in the proboscis sheaths, or in the walls of the 

 bothridia. The principal systems are: — (1) A very 

 compact bundle running " dorso-ventrally " between the 

 two bothridia, internal to the proboscis sheaths: this is 

 represented in fig. 3, PL I, in transverse section, and 

 diagrammatically in Text-fig. 1 by the darkly shaded 

 tract joining the bothridial suckers. (2) Fibres origin- 

 ating in the axial parts of the proboscis sheaths. Other 

 fibres of this series^ taking origin in the dorsal sheaths, 

 are inserted into both of the ventral sheaths, and vice 



