THE GREATER KANGAROO. 



and parts. In birds and reptiles, the allantois plays a primary 

 part in the respiration of the foetus. In the placental mammals, 

 its office, as a temporary respiratory organ, is secondary, but it 

 is essential as a means of transference of the hypogastric or 

 umbilical vessels, to the exterior enveloping membrane, or 

 chorion ; it, therefore, pre-exists to the placenta, and without it 

 the placenta could not be formed. The existence of a placenta 

 necessarily, therefore, infers the pre-existence of an allantois : 

 but the reverse of the proposition does not, therefore, hold good. 

 In birds and scaled reptiles, the allantois itself performs the 

 functions of the placenta, or vascular chorion j but in the kan- 

 garoo, and, perhaps, other marsupials, the allantois, when de- 

 veloped, does not serve as a medium for the organization of the 

 chorion, but remains, as in the oviparous vertebrata, an inde- 

 pendent vascular bag or coecum."* 



The skin and its appendages beneath the lower part of the 

 female's belly, is folded or doubled in such a manner as to form 

 an open pouch or bag, in which the young ones are contained 

 from a very early period, in which the process of suckling takes 

 place, and tp which, even for some time after they have acquired 

 sufficient size and strength to leave it, the little ones continue to 

 fly for safety and for succour. 



The greater kangaroo, though the largest of the marsupials, 

 produces only a single offspring at a birth, after a period of 

 gestation extending to thirty-eight days. The young, as observed 

 by Professor Owen, on the day of its birth, does not exceed one 

 inch two lines from the nose to the end of the tail j its eyes are 

 closed, and its integuments are of the colour and semi- trans- 

 parency of an earth-worm. Very justly has Mr. Ogilby declared 

 the most singular and important of the physical phenomena, 

 connected with the natural economy of marsupial animals, to be 

 this premature production of the young, brought forth in a 

 scarcely organized form, containing, as it were, the mere germ 

 of the future animal, before its senses are perfected, or its 

 members developed. As yet, however, we have no certain 

 * Abridged from Mag. Nat. Hist. (New Series), vol. i. p. 481. 



