BOEKBESPREKING. 271 
More than a mere variety, 
And varieties are not, as Darwin thought 
„Incipient species”.... they are nought. 
, 
They may regress 
or degress 
But never progress. 
They simply can’t offer the solution 
of really effective evolution. 
To the evolutionist no gladder scene 
Than a gamete forming a new gene 
In its time of preparation 
Which is called premutation. 
Because the addition of but one gene to its stock 
Though by no means putting it into a new frock 
Yet changes its inside in such a way, 
That it is certain to display, 
Some time after its wedding day, 
New characters dominating those of its mate 
Thus forming, at a tremendous rate, 
In fact all at once, to our admiration, 
New species by a process, called: mutation. 
De kruisingstheorie. 
The real cause of what is called evolution 
Is the mating of gametes of different constitution. 
Lorsy. 
TISCHLER, G., 1920, Ueber die sogenannten „Erbsubstanzen” 
und ihre Lokalisation in der Pflanzenzelle. (Biolog. Zen- 
tralb. XL p. 15—28, 1920.) 
Herhaalde malen is in de genetische litteratuur het zeer moeilijke 
vraagstuk der localisatie der „erfelijkheidsdragers” op den voor- 
grond gekomen en telkens weer op den achtergrond geraakt. Het 
