338 THE GROUSE IN HEALTH AND IN DISEASE 



rather of a cauliflower shape ; they contain rounded ova in which besides the 

 nucleus a second deeply staining body is sometimes seen. The vagina makes a 

 turn through about a right angle, and passing between the two ovaries, where it 

 receives the two oviducts, it travels back to the vitellarium, a somewhat pyramidal 

 body lying close to the posterior end of each proglottis. Certain unicellular glands 

 in this region of the female duct are probably shell-glands. 



There seems to be no walled uterus, but the fertilised ova are scattered through- 

 out the body embedded in the parenchyma. Each is a large oval cell with very 

 vacuolated protoplasm and a nucleus at one side and numerous yolk-granules. 



Monticelli describes the proglottides as longitudinally striated, and the 

 striations as due to the longitudinal muscles. These are certainly conspicuous in 

 section, although in our specimens the external striation was not very well marked. 



One striking feature of D. urogalli is the great extent to which the water 

 vascular system is developed. It is spacious and large in the anterior segments, 

 but in the posterior half of the body it becomes very much larger. The lumen of 

 the lateral canals increases, and the transverse duct which unites them at the 

 posterior end of each proglottis swells out amazingly. From being a slender duct 

 it enlarges to a great spherical chamber, of which the sides, which will rupture 

 when the proglottis drops off, are extremely thin. 



When the ova are squeezed out of a living ripe proglottis of D. urogalli, they 

 present the appearance shown in PI. LI., Fig. 4. Each egg contains a six-hooked 

 embryo which is much smaller than the egg-shell. Besides the six-hooked embryo, 

 the egg-shell contains two or three spherical bodies usually of about the same 

 diameter as the embryo, but sometimes smaller. These are apparently yoke-spheres 

 in course of absorption ; the remainder of the egg-shell is empty. The shape is 

 similar to that of the hooks figured in the sketches of Davainea embryos in 

 Blanchard's article 1 (PL LI., Fig. 4). 



The genus Davainea occurs in many birds, Cursores, Gallinacese, Columbinse, 

 etc., and much more rarely, in the form of Davainea madagascariensis (Dav.), in 

 the intestine of man. Little is known of their second hosts ; they are usually 

 believed to be insect larvae, centipedes or land molluscs. Grassi and Rovelli 2 con- 

 sider the intermediate host of the D. proglottina of the common fowl to be Limax 

 cinereus, L. agrestis, and L. variegatus. In this case the cysticercoid is fully 

 developed in the slug within twenty days. If the slug be swallowed by a fowl the 



1 "M(5m. Soc. Zool. France," iv. p. 420, 1891. 



2 "Centrbl. Bakter.," iii. p. 172, 1888. 



