160 MEMOIR ON THE REPRODUCTION OP THE OPOSSUM. 



her muzzle will always be concealed within the marsupium, while engaged in the work, 

 if she herself does that work. I should think the delicate touch of a watch-maker alone 

 fit to make the adjustment — so small is the stomal porule; — it is much more likely that 

 the young find the nipple in the incessant groping of the point of the oviform head. 



Mr. Owen saw his kangaroo put her nose within the pouch, and lick its edges — no one 

 will go farther in this discovery than that distinguished and admirable person has gone. 



My observation of this case does not settle the question of the duration of the uterine 

 gestation, though it will approximate it to the sixteenth or seventeenth day. Professor 

 Barton, in his letter to Mons. Roume computes it at from twenty-two to twenty-six days, 

 upon I know not what authority. Mr. Owen has convincingly shown that the kangaroo 

 carries in the womb thirty-nine days, post coitu. 



The rutting season here was in February. Professor Barton's didelph, which had five 

 young ones, as large as rats, two-thirds grown, when he bought them, on the 14th of 

 May, brought seven embryons into the marsupium on the 21st of the same month. He 

 says the uterine gestation is between twenty-two and twenty-six days, and that of the 

 pouch about fifty days; at which time they attain the size of a common mouse. — Letter 

 to M. Roume, T. & S. Palmer, Ph., 1806. " 



Mr. Owen's kangaroo had been giving suck to her young one just before the embryos 

 came into the pouch — which is evidence of a coincidence in the reproductive habits of 

 these two marsupials. 



As the five young ones which Dr. Barton procured were as large as mice, and freely 

 running about, they must have been some time detached from the marsupial life. But as 

 he says they are twenty-two days in the womb and fifty in the pouch, and in his speci- 

 mens, probably at least thirty days out of the sac, we have the inference that the concep- 

 tion took place one hundred days before the 4th of May; we suppose about the 24th of 

 January, and the second conception about the first of May. So that it may be the 

 rutting season extends from January to somewhere in May, say five months.* 



I shall endeavour very carefully to determine the duration of the marsupial life, and 

 should the definite facts come into my possession, I shall beg leave to communicate them 

 to the society in a supplementary note to this memoir. 



Addition. — Tuesday, May 11th — The sphincter marsupii cannot contain all the young 

 in the pouch — the half of two bodies hanging outside. No hair on the young animals. 

 They do not let go the nipple, this sixty-eighth day of marsupial life. 



Thursday, May 20th — Young still undetached; eyes still unopened. No reason to 

 suppose they have ever let go. This is the seventy-second day. 



Saturday, May 22d — An embryo was crawling on the body of its dam ; eyes slightly 

 open. It weighs four hundred and twenty-eight grains; having gained four hundred and 

 twenty-four and a half grains, since the 7th of March, seventy-four days ago. 



* A gentleman from Alabama says he has seen the very small marsupial young, in October, in that state. 



