The hypothesis of an internal passage from the uterus to the pouch— countenanced by some imperfect anatomical observations on the course of the round ligament to the abdominal ring, and the continuation thence of the cre master to the posterior part of the mammary gland, together with the primitive inverted condition of the nipple—is wholly refuted by more exact observations of the conditions of these parts. I was chagrined at the loss of so favourable an opportunity of determining, es visa, this interesting part of the problem ; for it had been my intention, if the symptoms of approaching pregnancy had been more marked, to have established a night as well as day-watch over the female; but by placing perhaps too much reliance on the observations on the preg nant kangaroo recorded in the 9th volume of the Annales des Sciences, in which the duration of four months is assigned to the uterine gesta tion of this species, I had not anticipated so speedy a termination of that process as resulted from my experiment.
In order, however, to remedy, as far as might be, this omission, it occurred to me that if the young kangaroo were detached from the nipple and deposited at the bottom of the pouch, any actions of the parent, by which its original transference from the uterus to the nipple had been aided or effected, might be instinctively repeated, and thus an insight be gained into their nature. As, therefore, the experiments of Messrs. Morgan and Collie seemed to show that this might be done without necessarily causing the death of the young one, I performed the experiment with the sanction and assistance of Mr. Bennett, then Secretary of the Zoological Society.
" Oct. 9th.—I examined the pouch of the female, and found the young one, now four days old, evidently grown, and respiring vigo rously ; it adhered more firmly to the nipple than was expected, requiring a continued gentle pressure to detach it : when that took place, a minute drop of whitish fluid, a kind of serous milk, was expressed from the nipple. No blood followed, nor anything to indicate a solution of organic continuity ; the extremity of the nipple was small, not swollen as in Mr. Collie's case. The young one moved its extre mities vigorously. It was deposited at the bot tom of the pouch, and the mother was left and then carefully watched. Soon after this was done she seemed uneasy, was often scratching the exterior of the pouch, and every now and then dilated the cavity with her two fore paws, grasping the sides of the aperture, and pulling them in contrary directions, just as in drawing open a bag; she then inserted her muzzle pretty deeply into the pouch, moving her head about as if to lick off something from the interior, or perhaps to move the little one She kept her nose in the pouch sometimes for half-a-minute. I never observed her to put
her fore-legs, or either of them, in the pouch ; they were always occupied in keeping open the mouth of the pouch, while she was at work with her mouth within it. She generally con cluded by licking the mouth of the pouch, and occasionally she stooped down to lick the cloaca, which she could reach with ease. When she scratched the outside of the pouch it seemed as if to push up something that was in side towards the aperture. These actions she repeated at short intervals for about an hour ; she then lay down and appeared quiet. She had also lain down in the intervals of the above operation, but during that time never meddled with the pouch ; when stimulated to do so by some uneasy sensation, she always rose upon her hind feet, and then inserted her muzzle alternately into the pouch and vulva. Observing the freedom with which she could reach both these parts, I was led to believe that the mode of removal of the young from the vulva to the pouch was by the mouth of the mother. her fore-paws, in this case, would be used, not for the transport of the young, but for keeping the mouth of the pouch open for its reception, it being deposited therein by the mouth, and so held over a nipple until the mother had felt it grasping the sensitive extremity of the nipple.
This means of removal is consistent with analogy ; dogs, cats, mice, all transport their young from place to place with the mouth. In the case of the kangaroo, it may be supposed that the foetus would be held by the lips only, not the teeth, on account of its delicate con sistence. Whether this theory, suggested by witnessing the actions of the mother after an artificial separation of the Marsupial foetus, be correct, must be confirmed by actual obser vation. There is no internal passage from the uterus to the pouch :—the mouth of the vagina cannot be brought into contact with that of the pouch, either by muscular contraction in the living or by any force of stretching in the dead kangaroo :—as the young was proved by the result of this experiment not to have the power of itself to regain the nipple, a fortiori we may conclude that it could not transfer itself from the vulva to the interior of the pouch and to the apex of the nipple :—the fore-paws of the Kangaroo would not so effectually protect the tender embryo from the external air as the mouth, nor so safely ensure its passage to the pouch, notwithstanding that they are adroitly used in grasping objects, being similar, in respect of the extent and freedom of motion of the digits, to the fore-paws of the Rodents.