ORGANS OF GENERATION. 177 



and usually in front of the kidneys. The ovaria and testes are 

 usually placed symmetrically upon the two sides, and are of equal 

 size ; it is rare for the testis or ovarium of the right side to be situated 

 higher up than the left, as in the Ophidia and Blindworms (Anguis), 

 where their asymmetrical arrangement reminds us of that of the lungs 

 and kidneys of the same side. 



In all the naked Amphibia and among the Squamigera, as the 

 Ophidia and Sauria, the Ovaria are in the form of simple sacs or bags, 

 mostly of a rounded shape, e. g., Ichthyodea, Tritons, Salamanders, 

 and Ophidia, or of a more elongated form, e. g., Sauria, lined inter- 

 nally with a smooth mucous membrane, beneath which the ova are 

 developed, and externally invested by peritoneum. Occasionally, 

 as in the Anourous Batrachia, the ovaria are divided into lobes ; and 

 partitions projecting into their interior, form there cells within which 

 the ova are found. In the direction forward, each sacciform ova- 

 rium is provided with a round or sometimes tubular aperture for 

 the exit of the ova ; within the smallest and most primitive ova a 

 chorion, vitellus, and germinal vesicle may be clearly distinguished, 

 the latter being in the Naked Amphibia provided with numerous 

 small germinal spots. In the Squamigera the germinal spot is always 

 single. In the Chelonia each ovarium, as in Birds and Cartilaginous 

 Fishes, consists of a stroma, upon the free surface of which, namely, 

 that turned to the ventral side, the ova are developed. 



The Oviducts are two long membranous, frequently multi-contort- 

 ed tubes, which are kept in their place by folds of mesentery, and 

 are provided in the direction forward in some Reptiles, as in the Che- 

 Ionia, with an infundibuliform abdominal ostium, into which the ova, 

 after being detached from the ovarium, are received. In the Ba- 

 trachia the opening of the oviducts is placed at a great distance from 

 the ovarium, in the proximity of the heart. Strong and even mus- 

 cular fibres lie between the external peritoneal and internal mucous 

 membrane, and by means of these the oviducts are capable of exer- 

 cising considerable peristaltic movements like the intestines. Their 

 internal mucous membrane exhibits, chiefly in their lower or poste- 

 rior part, strong longitudinal folds or villi, upon which the albumen is 

 secreted, being the first investment which is here obtained by the ova. 

 The oviduct is usually more widely dilated in the posterior part. 

 Both oviducts open into the cloaca separately. A clitoris has been 

 found hitherto only in the Chelonia and Crocodiles. 



The Testes are of an elongated form in the Ichthyodea and Ophi- 

 dia, or rounded, as in the Frogs, Sauria and Chelonia, and frequent- 



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