MODIFICATION OF REPRODUCTIVE PROCESS 79 



the mother, (i) food-material for its nourishment and 

 (2) the oxygen needed for its living activity. In the 

 opposite direction there pass away from the blood of the 

 embryo into that of the mother the various waste materials 

 produced by the vital processes of the embryo. This 

 arrangement of interlocking blood-vessels, by which 

 interchange takes place between the blood of the mother 

 and of the unborn young, constitutes the greater part of 

 a very complicated organ known as the placenta, or in 

 the case of man as the ' after-birth," from the fact 

 that it is shed and got rid of soon after the birth of 

 the child. 



The young individual leads its pre-natal life in the 

 comparative safety and seclusion of the uterus, hanging 

 on to its wall as a parasite, its needs being ministered to 

 by the activities of the placenta. But it is already, from 

 the zygote stage on, a new self-contained individual, 

 possessing, though it may be in a latent form, all the 

 normal characteristics of its race. So long as the mother 

 remains in a normal state of health the young individual, 

 when once it has come into existence by the act of 

 syngamy, does not appear to be affected by her special 

 peculiarities. Thus it has been found possible to take 

 the eggs at an early stage of their development from the 

 uterus of a Rabbit belonging to a particular breed (Angora) 

 and transfer them to the uterus of a Rabbit of a quite 

 different breed (Belgian Hare). The eggs so transferred 

 went on with their development, and the young rabbits 

 when born were found to be perfectly typical (Angora), 

 showing no signs whatever of having been influenced in 

 any way by the peculiarities of the foster-mother in whose 

 uterus they had sojourned during almost the whole period 

 of their development. 



