350 FactSy Observations, and ConjeduHSf [Nov, 



informed you, when I had the pleasure of seeing you in Phila- 

 delphia, that I had, for several years, been engagea in an exten- 

 sive series of experimetits and observations relative to this 

 curious animal; this "prodigiosum animal," as Benzoo calls 

 it.* The result of my inquiries will be communicated to the 

 public in two memoirs, the second (and most difficult) of which 

 IS nearly finished. 



In the first of these memoirs, I shall detail, at length, the 

 general natural history of the animal ; examine its place in the 

 system ; it§ food ; its manners ; its geographical range through 

 the continent, 8cc. 1 shall also particularly notice the periods 

 of the intercourse of the sexes, and shall pursue the female 

 through the whole progress of what I call the uterine gestation, 

 which comprehends a period of between twenty -two and twenty- 

 six days. 



The other memoir will commence with the second term of 

 gestation, which I call the marsupial gestation. This, which 

 dates its beginning from the first reception of the embryons 

 from the uterus, into the raarsupium, bourse, or pouch, is much 

 longer than the uterine gestation, and comprehends, even in a 

 physiological point of view, by far the most interesting era in the 

 history of the animal. I have been so fortunate as to ascertain 

 the size and weight of several embryons immediately after their 

 exclusion from the uterus. One of them weighed only one 

 grain ! The weight of each of the six other young ones was but 

 little more than this. 



The young opossums, unformed and perfectly sightless as they 

 are at this period,/mt? their way to the teats by the power of an 

 invariable, a determinate instinct, which may, surely, be consi- 

 dered as one of the most wonderful that is furnished to us by 

 the science of natural history .f In this new domiciliumj they 

 continue for about fifty days ; that is, until they attain the size 

 of a common house-mouse (Mus musculus), when they begin to 

 leave the teats occasionally, but return to them again, until they 

 are nearly of the size of rats (Mus rattus), at which time th^y 

 seem to be no longer necessarily supported by the milk of the 

 mother, but eat meat and vegetables of various kinds. 



The female Didelphis Woapink sometimes produces sixteen 

 young ones at a birth. I have actually seen this number attached 



I have chosen, signifies " white face." I should, perhaps, havd preferred the Tusca- 

 roraor Cheerake names, Chaera^ or Seequa^ but that I know not the precise meaning of 

 these appellations. I may add, in this place, that the specific name of " dorsigera^^* 

 which Linnaeus has applied to another species of didelphis (the Mcrian opossum of 

 Pennant) is likewise exceptionable ; for I have discovered, that my Didelphis Woapink 

 often carries her young ones upon her back. 



• Lib. ii. p. 215. 



+ It is not true, as has been often assetted, that the mother, with her paws, puts the 

 young oncR into the pouch. In my first memoir, I shall show, to the satisfaction of 

 every one, that the conmion opinions on this subject are altogether erroneous. 



