440 GROWTH AND STRUCTURE OF MNIA SAGIN^TA. 



even in some which have spontaneously left the intestine and voided 

 their eggs. This varicose enlargement is to be seen most frequently 

 near the point where they open into the vas deferens or just at the 

 junction, and has been described by Platner, to whom we are in- 

 debted for the most thorough representation of these structures, as a 

 special hollow of irregular jagged form the " spermatic sinus." 



The Vas Deferens itself is a comparatively wide canal with a dia- 

 meter of about 0'025 mm. It runs from the external aperture the 

 porus genitalis across the joint almost as far as the uterus, yet not 

 in a straight course, but, as in related forms, with numerous more or 

 less close coils, which sometimes look as though they were enclosed 

 in a common sheath. I have never been able to observe any special 

 enlargement or seminal vesicle either in the vas deferens or inside the 

 cirrhus-pouch into which the former opens. In the posterior some- 

 what distended portion of the bottle-shaped cirrhus-pouch (about - 4 

 0*5 mm. long) are found a few irregular windings of the vas 

 deferens, which does not exhibit here its usual thick firm walls, but 

 is clad internally with a thick layer of fine chitinous points directed 

 backwards. This structure is obviously adapted for protrusion 

 during copulation, forming the so-called " cirrhus." 



The Cirrhus in Tccnia saginata is very short, so that one only sees 

 it slightly protruded from the porus genitalis. It must, of course, be 

 remembered that the porus genitalis of this worm leads first into a 

 deep (O22 mm.) wide pouch or funnel-like cavity, which I have 

 called the " generative cloaca," because, besides the vas deferens, the 

 vagina also opens into its narrow posterior end. 



The Cloaca originates by the external body- wall becoming swollen 

 into an annular lip round the common generative opening. In con- 

 sequence of this the pore comes to lie at the end of a sort of boss- 

 like protuberance, as in most of the other Cystotcenice, but here it is 

 unusually large, up to I mm. Transverse sections through the genera- 

 tive cloaca leave not the slightest doubt as to the nature of the swell- 

 ing. One sees not only (Fig. 144) how the cuticle is continued almost 

 unaltered into the interior, but can also follow the musculature of the 

 cortical layer out into the surrounding walls. 



My former statements, according to which the pore was surrounded 

 by a special sphincter, which shut off the internal cavity during copu- 

 lation, have been corrected by Sommer and Landois. In reality one 

 sees in the wall of the generative cloaca no muscular elements other 

 than the processes of the transverse fibres bounding the inner layer, 

 which, instead of intertwining, run out to the outer surface of the 

 cirrhus-pouch, and sagittal fibres, which penetrate the projecting lips 

 in a dorso-ventral direction. But in spite of the absence of a proper 



