372 



dent that the passage must be reformed anew at each succeeding 

 act of parturition. 



It has now been shown that in representatives of two genera 

 of polyprotodont Marsupials (Per am el es and Dasyurus) the 

 young are born through a direct median passage and further in- 

 vestigation will doubtless considerably add to the number. 



P u c h - Y u n g. 



Six is the normal number of young in the pouch in correspond- 

 ence with the existence of six mammae but it seems to often happen 

 that more young are born than can be accommodated, and as a 

 general rule more ova commence their development than ever reach 

 completion. In one instance twenty four blastodermic vesicles were 

 taken from the uteri of a single female. 



The new^-born young are of small size, measuring in the fresh 

 extended state 7,6 mm (snout to rounded hinder end of body) and 

 in spirit, G. L. 5,5 mm, H.h. 2,3 mm. They are in the living state 

 of a faint reddish tinge and semitransparent so that the beating of 

 the heart, the main blood vessels and certain of the internal organs 

 are readily visible through the thin integument. The lips are fused 

 laterally though the fusion does not quite extend to their anterior 

 limits. The mouth opening is small and somewhat lozenge-shaped. 

 It is bounded laterally by thickened everted margins, rounded and 

 distinctly limited below where they adjoin the similarly thickened 

 anterior margin of the lower lip, the whole recalling the "Schnabel- 

 schild" described and figured by Selenka^) for Didelphys. 



The tongue projects slightly from the mouth and is grooved 

 dorsally. The eyes and the small triangular ear-pinna are covered 

 by epitrichium. 



The fore-limbs are well advanced, digits 2 — 5 being provided 

 with long and sharp recurved claws. The hind-limbs are mere flat 

 paddles, without any indication of digits. 



A remarkable feature in the new-born young is the existence 

 between the fore-limbs of a large bladder-like swelling of unknown 

 function, which arises from the thorax and is attached in front to 

 the floor of the mouth. It is covered by epidermis and consists 

 internally of a fine vascular retiform connective tissue. 



A few hours after fixation to the teat, the lip fusion is com- 

 pleted and the mouth enlarged to form a relatively huge crater-like 



1) loc. cit. p. 157, Taf. XXVII, Figs. 4, 5 and 6. 



