322 GENERAL ORNITHOLOGY part ii 



the rectum proper and the urogenital compartment of the sewer. 

 The renal excretion is not watery as in mammals, but semi-solid, 

 and voided with the faeces, of which it forms part. 



The kidneys are capped by a pair of small yellowish bodies, the 

 suprarenal capsules or adrenals (Figs. 103, // 104, 105, d), the 

 nature of which is undetermined. They are chiefly interesting to 

 the practical ornithologist from their liability to be mistaken for 

 testes in examining specimens for sex (see p. 68). 



Male Organs of Generation. — The testis (Lat. testis, pi. testes, 

 a witness ; Fig. 105, a) or testicle has been already sufficiently noticed 

 as to its general appearance and position (p. 69). As said above, 

 it is the essential male organ, consisting of the primitive indifferent 

 genital gland (Fig. 103, e) in its highest state of development as a 

 tubular secretory organ, connected with the remains of the Wolffian 

 body as a part of its efferent structure {epididymis; Fig. 1 05, 5) and 

 with the original Wolffian duct as its ms deferens (Figs. 103, d, 105, 

 c), or efferent duct, by which the semen is conveyed to the cloaca. 

 The original glands normally remain paired, and both are usually 

 functionally developed to corresponding size, shape, and activity; 

 they remain in their embryonic situation in front of the upper part 

 of the kidneys ; and such difference of appearance as they present 

 under different circumstances is mainly seasonal. For birds, as a 

 rule, procreate only at particular times of the year, rarely having 

 more than one or two broods of young : the functional activity and 

 quiescence of the testes correspond, as the enormous swelling of 

 the gland during the breeding season is one of the peculiarities of 

 the bird's organ. This may be related to the absence, in birds, of 

 specially formed vesiculce seminales, or seminal reservoirs ; though 

 certain contortions and dilatations of the sperm-ducts which are to 

 be observed may imperfectly answer to detain the secretion until 

 circumstances render it available. The passage of the sperm-duct 

 is along the face of the kidneys, generally in company with the 

 ureters ; the opening is by a papilla upon the surface of the uro- 

 genital sinus. These papillose terminations of the sperm-ducts 

 are erectile to a degree, and answer the purpose of paired penes in 

 those birds which are not provided with better-formed copulatory 

 parts. In coitu the cloacal chambers containing the orifices of the 

 genital ducts are opened, and the more or less protruded papUlse 

 come in contact or close juxtaposition. In cases in which a penis 

 or two penes are developed, the urethral passage is a groove, never 

 a tube, though cavernous and even muscular tissue may be de- 

 veloped ; and in any case of such an intromittent apparatus, it has 

 cloacal invagination when not operative. These organs, in all their 

 variety, are of the sauropsidan, not mammalian, type ; though in 

 some respects the structure approaches that seen in the non- 



