THE CESTODA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 449 
The appearance of the scolex varies with the state of contraction, and the rostellum 
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 ARtoLa, viz. 66 cm. by 
75 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 Tanup#, Ludw. 
Hymenolepis, sp. (2). 
The Cestode here described was found in the intestine of the Ringed Penguin, 
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 :— 
Length of neck,” 6-12 mm. 
Width of “neck” at broadest part, ‘93 mm. to 1:13 mm. 
Length of segmented region, about 1 cm. 
Number of segments, about 40. 
Diameter of broadest segment, 1:21 mm. 
TRANS. ROY. SOC. EDIN., VOL. XLVIII, PART II. (NO. 22). 67 
