128 Zoological Proceedings of Societies. 



physiology of certain structures which have been hitherto unnoticed, and 

 of others which have been incorrectly or imperfectly described by former 

 investigators of this interesting branch of natural science. 



The authour first pointed out the anatomical peculiarities which he had 

 discovered in the dissection of the pouch and mammse of a young and 

 unimpregnated Kanguroo : by which it appears that, in the virgin state, 

 the two upper nipples only are found to be developed, and that beneath 

 each of these a minute circular aperture, resembling in appearance the 

 mouth of a follicle, occupies the exact situation in which the lower teat 

 is known to exist in the adult impregnated animal. The mammae are 

 described as consisting of double glandular structures on each side ; they 

 are situated directly behind the follicular openings already mentioned, and 

 are closely confined to the posterior surface of the integuments. Each 

 double mamma is composed of an upper and smaller gland, which is 

 attached by its excretory ducts to the already developed nipple, and of a 

 second and larger glandular substance from which no excretory duct could 

 be traced. The follicular apertures which occupy in the pouch Aie situa- 

 tion of the lower teats, form the external openings of cylindrical mem- 

 branous canals which lie imbedded in the substance of the larger and 

 lower mammary glands. Each of these membranous canals or tubes is 

 about three-fourths of an inch in length, and extends through nearly the 

 whole diameter of the larger gland which incloses it; the interior of the 

 tube is lined by cuticle, and the internal extremity is terminated by a 

 rounded papilla which projects into its cavity. 



In these papillae the authour found a perfect miniature resemblance to 

 the extremities of the lower teats in the adult animal, which teats he con- 

 siders to be formed, during the first gestation, by the complete eversion 

 of the membranous canals, and the consequent projection of their papil- 

 lary terminations. He further states, that by artificially everting the 

 parts, two perfect teats are produced in the precise situation of those 

 which are found in after life. It has been, however, ascertained that this 

 extraordinary change occurs only during the first gestation, since after 

 being once developed the teat remains permanently formed and pro- 

 jected. 



Having thus described the condition of the mammary glands in the 

 virgin animal, and the developement of the lower teats, the authour gave 



