MEMOIR ON THE REPRODUCTION OF THE OPOSSl'M. 157 



The first named specimens came into my hands about midsummer, while the larger 

 ones, those of 1S1.">. were in the depth of winter. It is probable that the former speci- 

 mens were weaned in March— and that the latter were nearly a year old, though Dr. 

 Barton thinks they attain full growth in about five months, and he speaks of their weigh- 

 ing eighteen pounds. — Letter to Bourne, page 15, note. 



I am now in possession of a male and female, for which I am under great obligations 

 to C. \V. Sharpless, Esq., who was so good as to cause search to be made for them at 

 his Seat, at Concord, Delaware county, twenty miles south-west from Philadelphia, and 

 to send them to me by a special messenger. 



A light snow having fallen on the 18th of February, the tracks of two of the animals 

 were followed to the hollow trunk of a tree, from which they were taken. 



I was accustomed, in my youth, to hunt the opossum, as a boyish frolic, and have 

 caught many of them. I never saw two in company, and I believe they are solitary 

 prowlers, except during the season of the copulation. 



The fact that they were captured in company, and in the same trunk, leads to the con- 

 clusion that they hail retired to the concealment for the rut; and this idea is confirmed by 

 the state of the sexual parts of the dam, which were red and very turgid, while the testes 

 of the male were also very heavy and large. 



They were taken on the 19th of February, and sent to me on the 27lh of the same 

 month. I had them carefully fed, and frequently examined the pouch of the female, in order 

 to discover whether any mammary development might indicate her being in gestation. 

 There was no enlargement of the mammffi on the 27th — not the least — nor was there any 

 "ii the 28th. I examined the marsupium with care, both by inspection and palpation, on 

 Monday, the 1st of .March, and on Tuesday, the 2d; on neither of which occasions could 

 I discover any siirns of increase. But on Wednesday, the 3d, the mamma? were visibly 

 and palpably enlarged. They were still larger on Thursday, the 4th, and, on Friday, the 

 5th, the) were hard and swollen. Saturday, the 6th, passed without my inspection, on 

 account of professional engagements, which made my visit to the stable court impossible; 

 but my servant, who had always held her while I examined the pouch, looked into the 

 marsupium, and assured me there was no embryo attached on Saturday. 



At 3 o'clock, p.m., on Sunday, the 7th. when I opened the pouch, the young were found 

 at. the teats. Here, then, there was a visible preparation made for the reception of the 

 young, in the development of the mammary glands j a fact that serves clearly to refute, if 

 refutation could be necessary, the notion of the ( Ihevalier D'Abo 1 ! die, cited and scouted 

 by Dr. Barton, that the embryo makes the teat wherever it happens to touch the surface 

 with its mouth. See Prof. Barton's letter to Rcimarus, page 1<>. 



The man who had care of her says, that whenever he looked at her, on the Saturday, 

 she was lying on her side, \s ith her nose turned inward between her legs, toward- the hells , 

 and she appeared so torpid that he supposed Bhe was sick — the more especially a- -lie 

 scarcely took any notice of his hand when introduced into the box. \i all other times 

 she was, and is now. very cross and Bnarling; and makes a Bhow of defending herself. 



It is fair, from the above, to infer, that the uterine gestation terminated on tin- nighl of 

 Saturday, the (ith, or on the Sunday forenoon, the 7th of March: Bixteen days after the 

 vor.. \. — :'.? 



