108 FOOT-NOTES TO EVOLUTION. 
serve to simplify some of the intricate problems to be 
explained, but surely no one believes that development 
can ever be referred entirely to such factors. The fact 
is that determinism, which is the most fundamental 
characteristic of inheritance, is manifested at every step 
of development, and there is certainly no escape from 
the conclusion that this determinism depends upon pro- 
toplasmic structure, and that this structure it is which is 
transmitted from generation to generation, and which 
forms the physical basis of inheritance. 
All really inherited characters must, therefore, be 
represented in the structure of the germinal protoplasm, 
and must consequently be present from the beginning of 
development. ‘We must consider it as a law derivable 
from the causality principle,” says Hatschek,* “that in 
the phylogenetic alterations of an animal form the end 
stages are not alone altered, but the entire series from 
the egg cell to the end stage. Every alteration of an 
end stage or addition of a new one must be caused by 
an alteration of the egg cell itself.” Ndagelit has ex- 
pressed a similar view in the following famous sentence: 
“ Egg cells must contain all the essential characteristics 
of the species as perfectly as do adult organisms, and 
hence they must differ from one another no less as egg 
cells than in the fully developed state. The species is 
contained in the egg of the hen as completely as in the 
hen, and the hen’s egg differs as much from the frog’s 
egg as the hen from the frog.” 
4. The remarkable tenacity of inheritance, as shown 
especially in reversions and the preservation of useless 
and embryonic characters through many hundreds or 
* Berthold Hatschek. Ueber die Entwickelungsgeschichte von 
Toredo, Arb. Zool. Inst., Wien, 1880, 
+ Nageli. Mechanisch-physiologische Theorie der Abstam- 
mungslehre, 1884. 
