]80 EDWARD MCCRADY, JR. 



of this time the mother paid no attention to her offspring, 

 offering no assistance, and leaving it entirely to its own 

 exertions. 



This was the first time anyone had seen a very young mar- 

 supial crawl up to the pouch by its own efforts, but as the 

 author had not actually seen the young emerge from the 

 urinogenital sinus, he could not prove that it was actually 

 newborn. The next question to be settled was : "What is the 

 earliest age at which the marsupial young is capable of crawl- 

 ing by its own efforts? 



Hartman ('17) made some experiments which answered 

 this question, but which he did not publish until 1920. He re- 

 moved embryos near term from the uterus, freed them from 

 their envelopes, and allowed them to crawl about over the 

 mother, " which they did for at least fifteen minutes." This 

 definitely established the fact that they are capable of this 

 complicated feat even before birth. 



The final link in the evidence was supplied on February 6, 

 1920, when Doctor Hartman and Mrs. Hartman both witnessed 

 the whole migration from the first appearance of the foetus 

 at the vulva until its attachment to the nipple in the poucn. 

 ' ' Unerringly the embryo traveled by its own efforts ; without 

 any assistance on the mother's part, other than to free it of 

 liquid on its first emergence into the world" (Hartman, '20, 

 p. 5). 



I have given this rather lengthy summary of the evidence 

 because it does not seem, to have found its way into the text- 

 books of zoology, and the impression that the mother places 

 the young in the pouch is still almost universal. This must 

 be due partly to the extremely immature appearance of the 

 newborn and the consequent difficulty of believing it possible 

 that such a foetus could accomplish so difficult a feat. It may 

 also be due in part to unsuccessful attempts by others to 

 demonstrate this ability in young removed from the pouch 

 for experimental purposes. 



I have performed such experiments many times, and for a 

 while without success. My first success came on an occasion 



