QUADRUPEDS. 



are imbedded, but they appear rather in the form of simple 

 cavities in the substance of the ovarium, than glandular 

 bodies like those of the mammalia *. The oviducts suffer 

 an enlargement in their course, and terminate by separate 

 openings in a common passage with the urine. 



It does not yet appear in what manner the ovum is per- 

 fected. According to Sir JOHN JAMISON, " the female 

 is oviparous, and lives in burrows in the ground f." Ac- 

 cording to Sir E. HOME, to whom we owe nearly all the 

 accurate information we possess, relative to the structure 

 of the marsupial and monotrematous tribes, " the yolk-bags 

 are formed in the ovaria ; received into the oviducts, in 

 which they acquire the albumen, and are afterwards im- 

 pregnated. The foetus is aerated by the vagina, and hatch- 

 ed in the oviduct, after which, the young provides for it- 

 self, the mother not giving suck J." All these, however, 

 must be viewed as mere conjectures, scarcely warranted by 

 the appearances of the organs which have been examined. 



If these animals are oviparous, and we can scarcely en- 

 tertain a doubt on the subject, as the eggs have been trans- 

 mitted to London, it would be interesting to know the 

 manner of incubation, and whether oviparous or ovovivi- 

 parous, the kind of food by which the young are nourished 

 immediately after birth. 



There are only two genera known, the species of which 

 are natives of New Holland. 



136. ORNITHORINCHUS. Duck-bill. Snout produced 



* The form of these cavities has induced Sir E. HOME to term them yolk- 

 bags. (Phil. Trans. 1819, p. 236.) They differ, however, from the organs so 

 named in birds, in not being external and pedunculated, while they agree 

 with the corpora lutea in their imbedded station. In the kangaroo, he as- 

 signs the office of producing the ovum to the corpus luteum, and the yolk to 

 the oviduct, while the uterus furnishes the albumen. 



f Lin. Trans, xii. p. 585. Phil. Trans. 1819, p. 238. 



