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, 
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