740 AVES. 



their base within the sphincter of the cloaca upon its inferior wall. The 

 fibrous cones are placed side by side, but not confounded together ; and 

 the right is smaller than the left no doubt to allow this organ, which 

 never becomes soft as that of quadrupeds, to be more easily folded back 

 into the cloaca. Secondly, of a fibro- vascular body, which constitutes 

 the bulk of the inferior aspect of the penis, and is continued to its 

 extremity. Thirdly, of a cellular portion, capable of erection, placed 

 beneath the skin lining the urethral groove. This last is doubtless the 

 first appearance of the corpus spongiosum, which in Mammifers com- 

 pletely encloses the canal of the urethra, while the two others represent 

 the corpus cavemosum. The whole apparatus, when not in use, is drawn 

 into the cloaca by two pairs of retractor muscles. 



(2096.) In Geese, Ducks, and many wading birds, such as the Stork, 

 the structure of the male intromittent organ is totally different. When 

 in a state of repose, it is lodged in a pouch under the extremity of the 

 rectum, and curved, so as to describe three parts of a circle. When the 

 penis is opened in this condition, it is found to be made up of two por- 

 tions, each composing half of its substance. The parietes of one half are 

 thick, elastic, and slightly glandular. The other presents internally a 

 great number of transverse grooves and folds. This latter portion during 

 erection unrolls itself outwards like a glove ; and at the same time, the 

 half first mentioned, introducing itself into the hollow cylinder formed 

 by the second, fills it up, and constitutes the firmest part of the organ. 

 Most of the grooves and folds visible during non- erection become much 

 less apparent when the penis is protruded ; and their direction being 

 oblique, they prevent it from stretching out in a straight line, but 

 oblige it to assume a corkscrew appearance. A deep groove runs 

 along the whole length of this singular organ ; and it is into the com- 

 mencement of this groove that the vasa deferentia pour the seminal 

 secretion. 



(2097.) The females of species whose males possess a large penis are 

 provided with a rudimentary clitoris of similar construction. 



(2098.) The female generative system in the feathered tribes offers a 

 remarkable exception to what we have as yet seen in the vertebrate 

 Ovipara. Instead of being symmetrically developed upon the two sides 

 of the body, the right oviduct, and most frequently the corresponding 

 ovarium, remain permanently atrophied, and, although they do exist in 

 a rudimentary condition, they never arrive at such dimensions as to 

 allow them to assist in the reproductive process. 



(2099.) The fertile ovarium presents in all essential circumstances 

 the same organization as those of the Reptilia, and is in the same way 

 attached by folds of peritoneum in the vicinity of the spine (fig. 369,/). 

 The contained ova are found in all stages of maturity ; and being con- 

 nected together by narrow pedicles, the viscus assumes a distinctly 

 racemose appearance. 



