6 CLASS MAMMALIA. 



second matrix protected the development of animals born 

 in a state of such considerable debility. 



While this theory was predominant, some observations 

 appeared from the pen of a French Officer of Artillery, in 

 1786, in favour of the proscribed notions : they are to be 

 found in the travels of the Marquess of Chastellux, and we 

 shall present them in an abridged form to our readers. 



Two Opossums, (Didelphis Vtrginiana,) male and fe- 

 male, were domesticated in the house of M. d'Aboville, in 

 1783 ; these animals copulated, and the effects were atten- 

 tively observed by that gentleman : in about ten days, the 

 edge of the orifice of the pouch grew thicker, a phenomenon 

 which afterwards grew still more perceptible. As the 

 pouch increased in size, the orifice widened. On the 

 thirteenth day, the female did not quit her retreat except to 

 eat, drink, and evacuate : on the fourteenth she did not 

 stir from it. 



M. d'Aboville then determined to seize and examine her: 

 the pouch, the aperture of which had widened before, was 

 now nearly closed; a slimy secretion moistened the hairs on its 

 circumference. On the fifteenth day, a finger was introduced 

 into the pouch, and a round body about the size of a pea 

 was plainly felt at the bottom. This examination was made 

 with difficulty, on account of the impatience of the mother, 

 who had before this been always very mild and tranquil. On 

 the seventeenth, she permitted a further examination^ and 

 M. d'Aboville discovered two bodies about the size of a pea. 

 There was, however, a great number of these young ones. 

 On the twenty-fifth day, they moved very perceptibly, yield- 

 ing to the touch : on the fortieth, the pouch was sufficiently 

 open for them to be plainly distinguished ; and on the 

 sixtieth, when the mother lay down, they were seen hang- 

 ing to the teats, some outside the pouch, some inside. The 

 nipple is about two-eighths of an inch in length ; but it soon 

 dries up, and at last drops off, after the manner of the um- 

 bilical cord, 



