MALE ORGANS OF BIRDS. 



243 



testes of the House-Sparrow, which commences with the glands 

 as they appear in January, when they are no bigger than pins' 

 heads, and ends Avith their full developement in April. 



It rarely happens that both testes are developed In exactly the 

 same degree: the left is commonly the largest; but sometimes 



118 



e 



1. January. 



2. Middle of February. 



3. Beginning of Marcli. 



4. Latter end of March. 



Urinary and male organs of a Cock. 



i. Middle of April. 



Testes of the House-Sparrow, xciv. 



the right exceeds the left; and I have seen an example, in a 

 Rook, where it alone had taken on the action of sexual increase, 

 and had acquired a bulk compensating for the want of develope- 

 ment in the left testis. 



In most Birds, the only appearance of an epididymis, fig. 117, 5, 

 is a remnant of the primordial kidney, fig. 108, c. This part fre- 

 quently presents a colour strikingly different from that of the 

 testes : thus it has been observed in the Bustard and Curassow to 

 be black ; in the Cassowary, yellow ; and in the Demoiselle {An- 

 thropoides Virgo) to be of a green colour. In the Ostrich the 

 epididymis is folded upon itself at the side of the testis. 



The vas deferens, fig. 117, c, commonly passes down to the cloaca 

 by the side of the ureters without undergoing any remarkable con- 

 volution ; but in the Common Cock it is bent upon itself in short 

 transverse folds from side to side almost from its commencement ; 

 the folds gradually but slightly increase as they approacli the 



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