176 EDWARD MOCRADY, JR. 



The amnion and the allantois are exceedingly thin and deli- 

 cate. If the surrounding fluid is removed, the allantois will 

 usually break under the weight of its own contents. The 

 amnion is so close-fitting and thin that a single stroke of the 

 foreleg will rip it open. These two membranes are corre- 

 spondingly torn to shreds very early in the course of parturi- 

 tion, and are usually left in fragments in the vaginal cul-de-sac 

 and urinogenital sinus, though some fragments may some- 

 times be still adhering to the foetus when he emerges. No 

 such fragments are ever found in the lateral vaginal canals, 

 for the foetus does not pass out that way. 



On emerging from the vulva the newborn is thus either en- 

 tirely free of its membranes, or attended only by fragments 

 of the amnion and allantois. The statement sometimes made 

 that no navel is visible at this time is due either to special 

 use of the word 'navel' or to failure to look in the right place. 

 There is no depression, but the interrupted epidermis and the 

 torn end of the urachus are always distinctly visible a short 

 distance above the tip of the phallus (fig. 56). In this posi- 

 tion the navel, tends to be concealed by the hind legs and the 

 t'ail (fig. 55), and careful inspection under the dissecting 

 microscope is necessary to identify it. 



The migration to the pouch. The method by which the new- 

 born marsupial gets from the urinogenital sinus to the pouch 

 has long been a subject of dispute, and though exact informa- 

 tion with reference to the opossum has been available for 

 some time (Hartman, '20), a large number of naturalists 

 remain somehow unconvinced. 



The original theory, and one which is still widespread today, 

 is that the mother picks up the newborn young with her lips, 

 places it in the pouch, and holds it there until it is attached 

 to the nipple. 



Middleton Michel published in 1847 what purported to be a 

 first-hand account of parturition in the Virginiana opossum. 

 I do not mean to reflect upon the good faith of Doctor Michel's 

 report, but in the light of subsequent observations by several 

 others, I think it possible that he was misled by appearances 



