THE GENERATIVE APPARATUS OF BIRDS. 889 



acute angle, named the fourchette; tliey are covered exteLaUyrth hair The ^,?»^ 



oJZ rirofthfrestibu'll ™^"''-™3-«' - ^^-* "/ ^-'''"'^e, pour their secretion 

 Mamm^.-These are pectoral, and two in number. In their centre thev nresent an 



CHAPTEE III. 



GENEEATIVE APPAEATUS OF BIEDS. 



1. Male Generative Organs. 



The generative organs of the male are the testicles, and an excretory apparatus much 

 simpler than that of mammals. 



Testicles.— These organs are placed in the sublumbar region of the abdominal cavity 

 behmd the lungs, and below the anterior extremity of tlie kidneys. Their form is 

 usually oval, and their volume varies with the different species, as well as at different 

 seasons ; at the breeding season they are greatly developed. 



Excretory Apparatus. — In biixls there is not, properly speakmg, any epididymis The 

 vas deferens passes from within the posterior extremity of the testicle, is directed in a 

 flexuous manner backwards, draws near to the ureter on its own side, going along the 

 kidney with it, and arriving at the cloaca, where it terminates by an orifice to be alluded 

 to hereafter. In the Duck, it has near its termination a small oval vesicle, always filled 

 with spermatic fluid. 



Organ of Copulation.— This varies with the species. In the GaUinaese, it is only 

 a small papilla placed below, near the margin of the cloacal opening, and between the 

 two orifices of the deferent canals. This papilla is traversed by a furrow through which 

 the semen flows. In the Palmipedes, this organ is much more developed, and is 

 peculiar. Contained within a tubular cavity in the cloaca, it is protruded externally at 

 the moment of copulation by the eversion of this cavity, like a finger out of a glove ; it 

 then appears as a long pendant appendage, twisted like a cork-screw. 



2. Generatice Organs of the Female. 



The development of the young animal taking place external to the female, the 

 generative organs are limited to that producing the ovum, and the duct through which it 

 passes on leaving the ovary. 



Ovary.— In birds there is only one ovary, which is situated on the left side, the right 

 one becoming atrophied very early in nearly all species. This ovary is situated, like the 

 testicles, in the sublumbar region of the abdominal cavity, and constitutes a more or less 

 voluminous body, composed of a variable number of ovules in process of development : 

 some very young, little, and white; others more advanced in age, being larger and 

 yellow in colour. The ova are enveloped in a very vascular cellular membrane, which, 

 when they are ripe, splits in a circular manner, following an equatorial line, and permits 

 the escape of the essential part of the egg — the yellow (yelli), or vitellus. 



Oviduct. — This duct is long, very wide and dilatable, and very flexuous. It begins, 

 near the ovary, by an unfringed pavilion, and terminates in the cloaca by a somewhat 

 narrow oi-ifioe, which is considerably widened when the egg passes through it. The egg, 

 composed, on entering the oviduct, of the fundamental part named the yelk, or vitellus, is 

 enveloped in an albuminous sphere during its progress towards the cloaca, and after- 

 wards with a protecting shell. The oviduct of birds is, therefore, something more than 

 an excretory canal, as it participates in the formation of the ovum. It is composed of 

 three membranes : an external, serous, maintains the tortuous tube ; a middle, muscular ; 

 and an internal, mucous. 



