1823.] relative td the Generation oftM Opossum. dSl 



to the teats ; but never a greater number.* When they ar6 first 

 excluded from the uterus, they are not only very small, but very 

 obscurely shaped. The place of the future eyes is merely 

 liiarked by two pale-bluish specks : we see no ears ; in short, 

 the animal is a mere mishaped embryon. Its mouth, which is 

 afterwards to become very large, is, at first, a minute hole, 

 nearly of a triangular form, and just of a sufficient size to receive 

 the teat, to which the little creature adheres so firmly, that it is 

 scarcely^ matter of surprise, that Beverley f and other writers 

 have asserted, that the young are originally produced in the 

 marsupium, where they grow fast to the teats ; an opinion very 

 generally adopted in many parts of the United States. 



It is not true, that the young cannot be detached from the 

 mother, without the loss of blood. I can assert the contrary 

 from many experiments, made upon embryons weighing nine 

 grains, and upwards. I have fully satisfied myself as to all the 

 various circumstances, both in the structure and in the exertions 

 of the minute animal, which enable it, while yet a mere speck, 

 as it were, of living matter, to chng so firmly to the fountain of 

 its support. 



It is truly an interesting task to pursue the various steps in 

 the progressive evolution of the parts of the yoilng opossum, 

 while in the marsupium, and especially so long as it is necessarily 

 attached to the teat. It is natural to suppose that the all-care- 

 ful hand of Nature first evolves those parts, which are the most 

 immediately important to the animal. In this supposition we 

 are not mistaken. It is a long time before the embryon has any 

 occasion for the senses of sight and hearing : but a mouth and 

 the powers of deglutition, as well as of breathing, are necessary 

 to it, immediately after its exclusion from the uterus. Accord- 

 ingly, its mouth and nostrils are open; and, for a long time, all 

 the air which it respires is received through, and passes out of, 

 the latter channels. The stomach seems to perform its digestive 

 office in the embryon immediately after its first attachment to 

 the teat ; % and the wonderful little didelphis is by no means 

 the inanimate or the passive being some physiologists and natu- 

 rahsts have represented it.§ 



♦ I have been informed, that female opossums have been seen with more than sixteen 

 young ones, of the same birth. I cannot, however, place implicit dependence upon 

 this information, especially as I have never seen an opossum with more than sixteen 

 teats. 



+ " The young ones (says this writer) are bred in this false belly, without ever being 

 within the true one. They are formed at the teat, and there they grow for several 

 tveeks together into perfect shape,'* &c. — (The History of Virginia, &c. p. 136. 

 London, 1722. 



:j; In an opossum weighing only forty -one grains, I have seen the stomach very consi- 

 derably distended with a white matter, or milk. But the milk that is afforded to the 

 embryons, for a few days after their first reception into the marsupium) is nearly pellu- 

 , cid, or transparent, 



§ Mr. Pennant says they adhere to the teats "as if they were inanimate, till they 

 arrive at a degree of perfection in shape, and attain sight, strength, and hair ; after 

 which they undergo a sort of second birth." — (Arctic Zoology, vol. i. p. 84.) 



