May, 1905.] The Nature of the Reduction Division. 
333 
chromatin as before and from two sources, therefore with some- 
what different hereditary tendencies. Evidently a fusion or 
mixing and doubling of nuclei generation after generation is 
impossible, especially if the chromatin is organized into definite 
chromosomes. A reduction division of some kind is the inevitable 
accompanyment of a conjugation process in the life cycle. This 
fact being recognized we may proceed to find out in what ways 
the life cycle may be established. Theoretically a number of 
possible modes may be developed and the reduction division 
established at three points in the life cycle. 
1. Suppose an organism with x chromosomes to give rise to 
zoospores which conjugate completely; the resulting zygote 
would have 2x chromosomes. If, however, reduction takes place 
at the first division or germination of the zygote, the new organ- 
ism would have the reduced or x number of chromosomes. The 
double number of chromosomes exists only in the resting stage 
of the zygote and the result is a simple sexual cycle, the gametes 
being produced without a reduction division (Fig. la). 
2. If an organism with a; chromosomes gives rise to con- 
jugating zoospores, the zygote will contain 2x chromosomes. 
