THE CESTODA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 253 



or slightly inverted posterior end. The bladder measures 32 mm. in length, and at its 

 widest part is 10 mm. in diameter. 



The incomplete specimen is of iiitei'est in so far as it shows a portion of the neck 

 invaginated within the bladder. Since this is the condition in which cysticerci usually 

 occur in the tissues of their host, the existence of another specimen in the fully extended 

 condition in such a situation is worthy of special note. 



The presence of these larval Cestodes in the subcutaneous tissue of an animal such 

 as Weddell's Seal is of particular interest. The hosts of adult Phyllobothria are, as 

 far as known, mostly Selachians. 



With regard to the question as to the probable host of the adult worm, Dr Bruce 

 has made the interesting suggestion that this may be the Grampus. He informs me 

 that Stenorhynchus leptonyx and Lobodon carcinophaga are frequently seen with large 

 gashes upon their sides, which he is of opinion may be due to the attacks of a Grampus 

 {Orca, sp. ?). He considers it likely that Weddell's Seal is liable to similar attacks, 

 and in fact that the whole seal may at times be eaten. The following birds are fond of 

 blubber, and devour the carcases of seals, viz. the Giant Petrel {Ossifraga gigantea), 

 Sheathbill {Chinois aiha), and Skuas {Magalestris MacCormicki and M. antarctica). 

 Such habits render them liable to infection with the bladder-worm in question, and it 

 is possible that the normal host of the adult occurs amongst these. 



Order TETRARHYNCHA, v. Ben. 



Family TETRARHYNCHIDiE. 



Tetrarhynchiis, .sp. (PI. II. figs. 15 to 18.) 



From the muscles of the Bonito [Thynnus 2^elamys Linn.) caught at Station 31, a 

 small number of cysticercoids of a Tetrarhynchus-Y\k& organism were found. These were 

 not enclosed in a bladder, but lay quite free in the muscles, the proboscides being in a 

 number of instances partially extruded. They were not in any instance fully extended. 



The specimens measure about 6 mm. in length and l| to If mm. in width. There 

 is a thick, firm, slightly wrinkled, glistening cuticle upon the exterior. A distinctive 

 feature is the entire absence of suckers at the anterior end. There are four slender 

 retractile proboscides bearing about sixteen longitudinal rows of closely set, recurved 

 hooks. The proboscides are connected with four well-developed muscular bulbs, such 

 as are characteristic of this group. 



At the posterior end there is a small spherical bulb which is retractile within a 

 cavity. In most examples the bulb is within, but in one or two instances it occurred 

 exserted, the body of the cysticercoid being constricted closely around its base 

 (fig. 15). 



Transverse sections of the bulb show it to contain a deeply staining connective 



(ROY. SOC. EDIN. TRANS., VOL. XLVIII., 451.) 



