ORGANS OF GENERATION. 123 



and Natatores. It appears to be very much developed in young 

 Birds, but dwindles in size so as to be scarcely apparent in adult 

 age ; still, however, it exhibits varieties of form and proportions. 

 Its function is not accurately known. At first sight it might be com- 

 pared to the anal sacs of the Mammalia, while some anatomists on 

 the contrary regard it as the urinary bladder of the Bird, but both its 

 position, and the certain fact that urine gets into it only by accident, 

 militate against this opinion. Furthermore, its equal degree of devel- 

 opment in both sexes is opposed to the view of its being destined to 

 receive in the female the seminal fluid of the male, and be thus anal- 

 ogous to the spermatheca in the female insect. 



ORGANS OF GENERATION. 



THE Generative apparatus in Birds, especially of the female, de- 

 parts very considerably from its conditions in the Mammalia, and 

 throughout the whole class exhibits a very close conformity of char- 

 acter with the type of organization in the inferior Vertebrata. 



The Female organs of generation are, as a rule, asymmetrically 

 disposed, being only fully developed upon the left side. The ovari- 

 um consists of a small stroma made up of a bed of compact fibres, 

 in which are situated the very small vitelline vesicles. It is situa- 

 ted in the lumbar region, and is attached to the superior or anterior 

 extremity of the left kidney, and partly also to the renal capsule. 

 The free surface, or that directed toward the abdominal cavity, is 

 disposed in transverse folds, from beneath which the vitelli gradual- 

 ly protrude during their growth, so that the ovarium soon assumes 

 the appearance of a cluster of berries supported upon pedicles or 

 stalks. The oviduct, spirally contorted like an intestine, arid at- 

 tached to a fold of the mesentery, descends parallel with the left 

 kidney, and commences by an open funnel-shaped or truncate abdo- 

 minal ostium, adapted for receiving the ova after they have been 

 detached from the ovarium. This part is called the infundibuhtm, 

 and after being continued into a narrower portion, the oviduct again 

 expands into a kind of ventricle, within which the vitellus obtains 

 its complete investiture of albumen, and external to that the calca- 

 reous shell ; the rest of the tube is termed vagina, and short and 

 narrow opens upon the left side of the cloaca. The mucous lining 

 of the oviduct presents well-developed longitudinal folds, and the 

 whole organ augments in length as well as in capacity during the 

 period of oviposition. There are only a few Birds that possess a 



