Experiments of Delage and Loeb 



Biologists, with a few exceptions, seem to be 

 agreed that these chromosomes are the carriers 

 of all that which one generation inherits from 

 another. Thus the cardinal facts of the sexual 

 act are, firstly, prior to fertilisation the male and 

 the female gamete each part with half their 

 chromosomes ; and, secondly, the fertilised cell is 

 composed of the normal number of chromosomes, 

 of which one-half have been furnished by each 

 parent. Thus the microscope shows that the 

 nucleus of the fertilised egg is made up of equal 

 contributions from each parent. This is quite 

 in accordance with the observed phenomena of 

 inheritance. 



But Delage has shown that a non-nucleated 

 fragment of the ovum in some of the lower animals, 

 as, for example, the sea-urchin, can give rise to 

 a daughter organism with the normal number of 

 chromosomes when fertilised by a spermatozoon. 

 Conversely, Loeb showed that the nucleus of the 

 spermatozoon can be dispensed with. Thus it 

 seems that either the egg or the spermatozoon of 

 the sea-urchin contains all the essential elements 

 for the production of the perfect larva of a 

 daughter organism. We are, therefore, driven 

 to the conclusion that the fertilised ovum contains 

 two sets of fully-equipped units. Only one of 

 these seems to contribute to the developing 

 organism. If this set happens to be composed 

 of material derived from one only of the parents, 



