MAMMARY ORGANS IN MARSUPIALIA. 773 



elongated and approximated, and the rima glottidis is thus 

 situated at the apex of a cone-shaped larynx, fig. 604, c, which 

 projects into the posterior nares, where it is closely embraced by 

 the muscles of the soft palate. The air-passage, b, is thus com- 

 pletely separated from the fauces, and the injected milk passes 

 in a divided stream on either side the larynx to the oesophagus. 



Thus aided and protected by modifications of structure, both 

 in the system of the mother and its own, designed with especial 

 reference to each other's peculiar condition, and affording, there- 

 fore, the most irrefragable evidence of creative foresight, the 

 small offspring of the Kangaroo continues to increase, from sus- 

 tenance exclusively derived from the mother, for a period of 

 about eight months. During this period the hind-legs and tail 

 assume a great part of their adult proportions ; the muzzle elon- 

 gates; the external ears and eyelids are completed; the hair 

 begins to be developed at about the sixth month. At the eighth 

 month the young Kangaroo may be seen frequently to protrude 

 its head from the mouth of the pouch, and to crop the grass at 

 the same time that the mother is browsing. Having thus 

 acquired additional strength, it quits the pouch, and hops at first 

 with a feeble and vacillating gait, but continues to return to the 

 pouch for occasional shelter and supplies of food till it has at- 

 tained the weight of ten pounds. After this it will occasionally 

 insert its head for the purpose of sucking, notwithstanding 

 another foetus may have been deposited in the pouch ; for the 

 latter attaches itself to a different nipple from the one which had 

 been used by its predecessor. 



Dr. Meigs 1 reckons the utero-gestation of a female Didelphys 

 Virginiana, which bred in captivity, as extending from the 18th 

 February to the 7th March — a period of seventeen days 2 — when 

 she brought forth thirteen young, which were found attached to as 

 many nipples. The mammae began to enlarge four days prior to 

 birth. On the 6th March she was observed to lay on her side 

 with her nose turned inward between her legs towards the belly, 

 and took scarcely any notice of her keeper's hand when intro- 

 duced into the box : the transit of the foetuses was probably in pre- 

 paration or operation at this time. The young, observed on the 

 7th, and which were certainly not in the pouch on the 5th, and 

 probably not until the night of the 6th, were naked, of a rose 



1 In a valuable memoir on the Reproduction of the Opossum, cclxxviii". 



2 Dr. Barton computed the utero-gestation of the Virginian Opossum at from twenty- 

 two to twenty-six days : his female brought forth seven young on the 21st of March ; 

 and had shortly before that time given suck to five young ones as large as rats. lxxx'. 

 p. 320. 



