THE CESTODA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 251 



The appearance of the scolex varies with the state of contraction, and the rostelhun 

 may be retracted so as to be concealed below the anterior margins of the suckers, and 

 thus appear to be absent. Similarly, the anterior proglottides, which in the extended 

 condition are rather long, with thick, overlapping posterior margins (described by 

 Ariola as " campanulate"), in the contracted condition become rectangular, short, and 

 relatively very broad. The maximum size occurring in the Scotia specimens is 40 cm. 

 by 5 '5 mm., which is considerably less than that given by Ariola, viz. 66 cm. by 

 7 "5 mm. This, which appears surprising in view of the large number of examples 

 in the collections, is probably due to breakages. The specimens occurred very closely 

 matted together, and there are numerous fragments without scolices. Ariola (1) has 

 given a summary of the chief features of this species. 



The following additional points have been made out in transverse sections. 



The longitudinal nerve cords, which are large and well defined, are situated about 

 one-fifth of the transverse diameter from the margin, external to the longitudinal 

 excretory canals. 



The central excretory canals are six in number, three each, right and left of the 

 middle line. 



Order CYCLOPHYLLIDEA, van Ben. 

 Family T.*;NIID^, Ludw. 



Hymenolepis, sp. (?). 



The Cestode here described was found in the intestine of the Rinoed Penouin. 

 Pygoscelis antarctica — locality, South Orkneys. It occurred in groups of from four 

 to twelve, having their heads within a small swelling upon the intestine of about the 

 size of a pea. The swelling, which had brownish granular contents, projected upon 

 the outer side of the intestine. The heads appeared, as far as could be made out, to 

 lie freely in the cavity formed by the swelling or cyst. This opened to the intestinal 

 cavity by a very narrow aperture through which the closely grouped necks of the 

 worms passed. 



The " heads" are of very irregular and variable form. This anterior region is best 

 described as a " pseudo-scolex." The "neck" is very long, and in most cases is at one 

 part enlarged in a long oval form. The segmented portion is nearly cylindrical — 

 not flattened — and, apart from colour, has quite an annelid appearance. The following 

 measurements were made : — 



Len<,'th of "neck," 6-12 mm. 



Width of "neck" at broadest part, '93 mm. to I 'IS mm. 



Length of segmented region, about 1 cm. 



Number of segments, about 40. 



Diameter of broadest segment, 1'21 mm. 



(ROY. SOC. EDIN. TRANS., VOL. XLVIII.. 449.) 



