March,-! DoYLE, A Note on Parturition in Perameles. 21^ 



1914 J ' J 



developed foetus, through the vaginal canal constitutes the 

 essential act. 



The theory that the marsupial embryo grows from the 

 nipple of the mother cannot hold ground, for several reasons — 

 (i) If the embryo were an outgrowth from the maternal nipple 

 there would be organic union between the embryo and mother. 

 The fact that the embryo can easily be detached from the nipple 

 amply disproves this point. (2) The embryo has been obtained 

 just after parturition has occurred, and before the mother had 

 placed it on the nipple. This is a conclusive piece of evidence, 

 and breaks down the line of demarcation between the two 

 types before-mentioned. 



The specimen which formed the subject of this investigation 

 was sent to the biological school of the Melbourne University. 

 The sender had already preconceived a theory bearing on the 

 subject of parturition, which he formulated in these words : — 

 " The embryo passes down on either side through what I take 

 to be the inguinal canal, and through the openings directly 

 into the pouch and on to the nipple, where it remains. The 

 opening is only patent in preparation for parturition, and then 

 begins to close, seen commencing on the left side of the 

 specimen " 



The animal on which this extraordinary theory rested, on 

 examination was found to be a fully-grown female specimen of 

 Perameles obesula. The pouch was in the normal position, 

 and on the wall of the pouch just below the nipples were two 

 openings, one on each side, that on the right side being larger 

 than that on the left, and being on a slightly lower plane. Thus 

 the openings were seen to be symmetrical neither in size nor in 

 position. This is an important point, as an opening for such 

 a function as parturition would of necessity be symmetrical 

 from the very order of things. 



In carrying out this investigation the objects kept in view 

 were — 



(i) To find out where the openings in the pouch led to. 

 (2) To ascertain what connection, if any, they had with 

 parturition as it normally occurred in the animal. 



The following procedure was carried out : — The pouch was 

 split open longitudinally in the median line, and the flaps turned 

 aside. Then the skin, except that in the region of the anus, 

 vagina, and pouch, was stripped off, leaving exposed the 

 muscles forming the abdominal wall. When this was done, 

 the pouch itself was carefully dissected off the muscles, but the 

 position of the holes in the pouch to the underlying muscles 

 was carefully noted. It was then noticed that the muscles 

 attached to the pubic symphysis were torn and ragged and had 

 gaps in them, and that the openings in the pouch led into these 



