348 CLASS xvi. 



not lie exactly in the middle, but more to the left side, on the 

 inside of the anterior part of the kidney of that side. It is a flat 

 organ, with transverse folds on the ventral surface in which the 

 eggs are formed. Those eggs which are nearest the surface are 

 most developed and thus higher coloured and larger; the vascular 

 envelop with which they are covered forms a cup (calyx), which 

 at its base extends into a pedicle, so that the ovary, when many of 

 its eggs are becoming ripe, has a clustered appearance. In the 

 middle of the calyces a whitish ring or girdle is seen, indicating 

 the place where the capsule of the egg, when the development in 

 the ovary is completed, bursts open ; when the egg has escaped the 

 cup contracts and shrinks up 1 . 



The egg is now received by an oblique elongated opening at 

 the upper part of the oviduct, which is capacious and funnel-shaped 

 (infundibulum) . Gradually becoming narrower the long oviduct 

 proceeds tortuously downwards; its internal surface presents longi- 

 tudinal folds. In this part of the oviduct the white of egg is secreted, 

 which is deposited in layers around the yolk. Then a wider part 

 succeeds, in which the egg tames longer and the calcareous shell 

 is formed. This part, covered internally with large villi, is named 

 the uterus by some writers; whilst the last portion which opens 

 into the cloaca and transmits the egg now completely formed is 

 named by them the vagina. They are not however distinct organs, 

 but only divisions of a single tube. The bowel-shaped oviduct is 

 supported by a fold of the peritoneum and attached to the spinal 

 column. In some few birds only is there a clitoris present in the 

 cloaca*. 



(Beitr. zur Gesch. der Thierwelt, 1825, in. s. 57, 58). The presence of two ovaries in 

 adult birds is therefore to be regarded as the persistence of an earlier state (Hemmungs- 

 bildung, Arrest of development). 



1 The ovary of the fowl has been often figured, see, for instance, R. DE GRAAF 

 Opera omnia, 1705, Tab. xvm. p. 253 ; GEOFFROY ST.-HILAIRE Mem. du Mus. x. P. 4, 

 fig. i M. M. CARUS Vergl. Zootomik. Tab. xvi. fig. 15; LEREBODLLET Recherches 

 sur les organes genitaux des anim. vert., Nov. Act. Acad. Cces. Leop. Carol, xxiu. P. i, 

 1851, PI. 3, fig. 43, PI. n, fig. no, &c. 



2 In the ducks and the struthious birds ; see on the last named, where this organ 

 presents a groove on the surface like the penis, MUELLER Ueber zwei verschiedene Typen 

 in dem Ban der erectilen mdnnlichen Geschlechtsorgane ~bei den strausartigen Vogeln. 

 (Abhandl. der ATcad. der Wissensch. zw Berlin, 1836, Physik. Math. EL) s. 21, 22, 

 Tab. i. figs. 3, 4. 



