40 GENERAL HISTORY OF BIRDS. 



its upper extremity. The anatomy of the entire apparatus has been employed 

 with advantage in the natural classification of birds, but to fully describe the mor- 

 phological details thus used in this brief chapter Avould be quite out of the 

 question. 



Reference has already been made above to the kidneys and ureters. The 

 former are functionally preceded by the "Wolfiian bodies," structures that 

 subsequently almost entirely disappear in both sexes, especially in the female. 

 The paired kidnej^s when fully developed, are large and elongated, and present 

 a lobulated appearance. In birds the urinary secretion is only semi-fluid and 

 soon hardens. 



THE GENERATIVE SYSTEM. 



The organs of the generative system in birds closely resemble -what we 

 find in the Reptilia. The testes, oval in form and two in number, are situated 

 just in front of the kidneys in the pelvic cavity. Through the vasa deferentia 

 they communicate with the cloaca, to which receptacle the spermatic fluid, 

 during the breeding season only, is conveyed. A true copulatory organ in the 

 male is, as a rule, absent, it being found, however, in rudimentary form in 

 Storks, Spoonbills and their allies. It is far better developed in some of the 

 Ostriches, the Anseres, and in Guans and Curassows; — best of all, perhaps, in 

 the two-toed Ostrich, a bird which seems to have been particularly favored in 

 this regard. Passing to the female, we are to note that it is only the ovary and 

 oviduct of the left side that is developed and becomes functional during the 

 breeding season. These parts are frequently entirely absent on the right side, 

 or else much reduced. Rare exceptions to this rule may occur. The writer 

 recalls the collected specimen of a female blue jay he once examined in the 

 breeding season wherein the functional ovary was upon the right side instead 

 of the left. During the breeding season the presence of the ovary may be 

 easily detected as a racemose, whitish and flattened mass, anterior to the renal 

 organs; and the oviduct, greatly coiled upon itself, presents three divisions, 

 viz: the abdominal ostium, the coiled glandular part which secretes the albu- 

 men, and the part corresponding to the "uterus," and egg-shell producing or- 

 gan. In those species where the copulatory parts are present in the male, 

 there are clitoris-like structures in the female of the same species. 



CHAPTER III. 



ecology of birds. 



Contrast between uniformity of structure and variety of habits. 



As has been shown, there is great uniformity in structure among birds 

 contrasting remarkably with the range of difference in other classes 



