98 
H aecker . — The Reduction of the 
a single one ; and, further, that the second division is accom- 
plished in this way — that every two elements, lying one 
behind the other in the original chromatic thread, are dis- 
tributed in the two nuclei. 
I should like to repeat a scheme, of which I have made 
use in a former paper and which has lately been also accepted 
by Riickert. If we signify the chromosomes (Idants of 
Weismann), lying one behind the other in the connecting 
thread, by a, b,c,d the scheme of the longitudinally split 
thread is written thus : 
abed.... 
abed.... 
For example, if the ‘ normal ’ number of chromosomes is 
twenty-four, the scheme is the following : 
abed.... wx 
abed.... wx 
When the generative cell begins the process of division, from 
this thread are separated the well-known tetrads ( Vierer- 
gruppeji ) : 
ab cd wx 
ab cdi wx 
In the first division they are disjoined in this way: 
I. ab cd wx ( = egg-nucleus) 
II. ab cd wx ( = first polar body). 
In the second division the double elements are disjoined 
into their units (reduction-division). From every pair, there- 
fore, one element passes into the one nucleus, the second into 
the other. It has not yet been decided if there is a constant 
rule in the distribution, and I think it will never be decided ; 
but we could assume, for example, that the distribution takes 
place in this way : 
t 
1 
t 
4 
