摘要:

Summary.The biology of the pouch‐young (mammary foetus) is considered in a graded series of stages ofDasyuruscommencing with the new‐born, still unattached young and ending with the fully developed animal at the time it leaves the maternal pouch (at the age of 4 to 4 months) and capable of fending for itself. The series has been divided for convenience into seventeen stages, labelled A‐P, and the growth, external appearances and eruption of teeth has been fully considered.The problem of the migration of new‐born young to the pouch, their attachment to the nipples, and the mode of lactation and its duration have been considered, together with some comment of the supposed mammary compressor action of the cremaster muscles.The internal structure of the new‐bornDasyurushas been described in detail, special emphasis being laid on the precocious development of certain structures which are considered necessary adaptational machinery for the insurance of survival of the young in its unusual environment and more particularly those features required for the sole purpose of ensuring its safe arrival in the pouch, its becoming attached to a nipple and the certitude of its receipt of milk without hindrance to its respiration.Notable at birth are (i) the relatively advanced state of the fore‐limbs, (ii) the presence of deciduous claws upon the manual digits and their later replacement by definitive claws, (iii) the presence of the oral shield as a specialization upon the muzzle, (iv) the unique cervical swelling, (v) special features of the tongue and larynx, with the intranasal epiglottis (vi) the reptilian state of the lungs, (vii) the advanced condition of the stomach and duodenum compared with the rest of the gut, (viii) the state of development of brain and sense organs, the olfactory parts being especially forward in development, together with those parts of the nervous system necessary for controlling the movements of the fore‐limb, sucking and respiratory movements, (ix) the indifferent state of the gonads.Throughout comparison has been made with the new‐born of other marsupials, so far as these are known, and features common to them all or peculiar toDasyurushave b

ISSN:0084-5620    

DOI:10.1111/j.1096-3642.1955.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY