g6 H aecker. — The Reduction of the 
one may perhaps be justified in directing their attention to 
the results attained by German zoologists. 
I will confine myself in the following pages to the two 
questions ; — at which point and in what manner the reduction 
of the number of the chromosomes takes place. 
Strasburger attempts to show that in the Angiosperms ‘ the 
reduction takes place directly, both in the mother-cells of the 
pollen and in the mother-cell of the embryo-sac, and in such 
a manner that the reduced number of chromosomes is at once 
apparent in the prophase-stage.’ The reduced number is 
retained during the subsequent divisions until the formation 
of the nucleus of the ovum and of the spermatic nucleus. 
Then the original number of chromosomes is re-established 
by the union of both elements. 
To give an example, Guignard has shown that in Lilium , 
in all the nuclear divisions which are to be found in the pollen- 
sac and in the ovule, twenty-four chromosomes are visible. 
The framework of the resting nucleus of the pollen-mother- 
cell and of the embryo-sac mother-cell is therefore constructed 
of twenty-four chromosomes ; yet in the next prophase it 
nevertheless uniformly gives rise to only twelve chromo- 
somes. 
How is this reduction accomplished ? Strasburger inclines 
towards the theory of the individuality of the chromosomes — 
that is to say, he would like to assume that these are ‘ always 
the same chromosomes, which make their appearance over and 
over again in the repeated divisions.’ Therefore he assumes, 
in order to explain the direct c reduction,’ that the diminution 
of the number of chromosomes by half is due to the fusion 
into one of two chromosomatic individuals. 
I believe that by assuming such a fusion the process of 
reduction is robbed of all theoretical significance, as far as 
such significance bears upon the theory of heredity. But 
I will not touch on this question, preferring rather to keep 
to the main subject. 
Strasburger believes it to be proved that also in the mother- 
cells of the ova and spermatozoa of animals the reduction 
