F. J. Meggitt 
45 
of the hooks however cannot be seen until the head is teased apart and the 
hooks spread out. Surrounding the rostellum is a thick ridge within 
which it may be retracted. 
The rostellum itself (PL VI, figs. 1 and 4) is small in comparison 
with the size of the head. Its length is 0-0462 mm. and its diameter 
0-15 mm. It consists of a simple apical protuberance composed of the 
usual parenchyma, bearing the double circle of hooks just mentioned 
and surrounded by a circular ridge (r.r.). In the centre of the pro¬ 
tuberance is a hemispherical core (r.c.), 0-074 mm. in diameter and 
0-0247 mm. long, having a slightly muscular appearance. I am 
in doubt as to the function of this core. At no point does it reach 
the exterior, so that it cannot be used for purposes of fixation: it is 
certainly not sixfficiently muscular to be used for the protuberance of the 
rostellum, and furthermore is surrounded by a very definite membrane 
so that muscles cannot penetrate to its interior. Lack of material and 
the consequent lack of preparations makes it impossible to proceed any 
further in the elucidation of this organ. 
I min 
Fig. 2.—Longitudinal vertical section through a proglottis. 
Anteriorly, the proglottides are many times wider than long, but 
more posteriorly their length increases more rapidly than their width. 
Mature proglottides measure 1-546 mm. long x 1-774 mm. wide, and 
proglottides ready for detaching are 1-7166 mm. long by 2-566 mfn. wide. 
The posterior edge of each proglottis overlaps the anterior margin of 
the succeeding one, slightly at first, but to an ever increasing extent 
posteriorly (Text-fig. 2). 
Musculature. 
The musculature consists of three distinct layers of longitudinal 
muscles alternating with three layers of transverse muscles, the 
innermost layer being transverse. In the more posterior part of the 
proglottis, the muscles, more especially the longitudinal ones, are 
surprisingly feebly developed: in proportion as sections are taken 
