1046 - DR. F. E, BEDDARD ON 
much thicker layer of circular fibres.. The inner layer is twice, 
or in parts thrice, the thickness of the outer layer. The imner 
circular layer ceases with the diminution in diameter of the 
cirrus-sac on its way to the exterior; the inner oval region is 
alone thus fortified. The outer muscular layer, however, con- 
tinues to the distal extremity of the cirrus-sac and its narrower 
projection. Outside of these muscle-layers the cirrus-sac is 
enclosed within a single layer of rather large vesicular cells with 
a prominent nucleus. It appeared to me that this layer was 
continuous with the epithelium of the ensuing vas deferens, 
though special to the cirrus-sae in its peculiar structure. The 
cirrus-sac, as usual among the Cestodes, contains delicate muscular 
fibres and nuclei within it in addition to the cirrus. In the 
younger stages in the development of the cirrus-sac the sac has 
Text-figure 4. 
Moneecocestus erethizontis. 
A proglottid viewed in its entirety, to show the position and shape of the 
ovary (ov.) and yitelline gland (v.g.). 
ci. Cirrus-sac. w.v. Water-vascular tpbe. 
more delicate walls in the rounded part of it, while the region 
leading to the genital cloaca has thicker muscular walls; the 
precise reverse occurs in the adult sac. The cirrus itself lies in 
a perfectly straight line in the adult cirrus-sac, and is of even 
calibre throughout when not distended with sperm; there is 
nothing in the nature of a vesicula seminalis within the cirrus- 
sac such as has been described in many forms. But when 
charged with sperm, dilatations are formed locally which are 
therefore to be regarded merely as local turgescences due to the 
enclosed sperm, and not, as representing a definite dilatation 
on the course of the duct, such as is the receptaculum upon 
the course of the vagina in this and other tapeworms. In 
