Phenomena in some Tasmant'aii M>irsupiah. 227 



remarkable cnouf;Ii. llartmnn * luuiicl, on one occasion, just 

 alter parturition, in the pouch of a female Virginian opossum 

 eighteen foetuses endeavouring to accommodate tliemselves 

 in a pouch which normally holds eleven ; while tor JJasyurus 

 viveriiniis, in which the pouch normally holds six teats, Hill f 

 recoids two speciHc instances in which there were found 

 respectively eighteen and ten foetuses just after parturition. 



It is interesting to note that a similar condition of affairs 

 appears to he normal for the rare Tasmnnian polyprotudont 

 marsupial Surcophilus ursiniis (''Tasmanian devil"). Up to 

 the present I have not been able to obUiin a female with 

 developing uterine embryos; still I have been lortunatt- in 

 receiving one in which ovulation had occurred but just 

 previously. In the very much enlarged and congested uteri 

 I found some twenty-one newly discharged ova — ten in the 

 right and eleven in the left. It was unfortunate that these 

 had not been fertilized, but the large number is of significance 

 when it is remembered that, in this genus, the maximum 

 pouch accommodation is four, and that it is not uncommon to 

 find but two of the teats occupied. 



So far such records extend only to polyprotodont marsupials, 

 in which this featuie is admittedly regarded as primitive. It 

 is therefore somewhat surprising and interesting to find that 

 a similar condition of affairs exists in the diprutodont Paeudo- 

 chiriis cooki. 



In the ancestral condition the pouch of Fseudochirus is a 

 small subcircular depression, measuring about 8 mm. in 

 diameter. Posteriorly it is bound by a thickened ledge, 

 while anteriorly the margin is thinner, and here the floor of 

 the pouch is somewhat depressed below the surface and 

 extends a few millimetres forward into the abdominal wall. 

 Within the pouch are four teats — an anterior pair and a 

 posteiior pair. Both pairs are confined to (he posterior half 

 of the pouch. The teats of the anterior are separated by a 

 greater lateral distance than those of the jjosterior — an arrange- 

 ment which recalls the horseshoe-like disposition of the teats 

 in the pouch of Dasi/urns (Hill and O'Donoghue, 1913). 

 The teats are all snuiU and approximately equal in size at 

 this stage. 



I have many specimens contidning well-advanced uterine 

 embryos, aiul they all agree in thrir pouch-features. In a 

 rejncsentative female {I's. couki, A. 30/7/20) both uteri were 



• Iliirtman, C. G., "Studies in the Development of the Opo.-iSiuu 

 DidelpJn/a virf/im'<ina. — V. The Phenomenon of I'aitiiritinn," Annt. Koc. 

 vol. xix." (liL'i)). 



t Hill. J. I'., he. fit. (lOOO). 



15* 



