198 



REDUCTION OF THE CHROMOSOMES 



E. REDUCTION IN UNICELLULAR FORMS 



A reduction of the number of chromosomes as a preparation for 

 conjugation in the one-celled forms has not yet been certainly deter- 

 mined, but there are many facts that render it highly probable. In 



C 



D 



Fi S- 99- Conjugation of Closterium. [KLEBAHN.J 



A. Soon after union, four chromatophores. B. Chromatophores reduced to two, nuclei 

 distinct. C. Fusion of the nuclei. D. First cleavage of the zygote. Jl. Resulting 2-cell stage. 

 /. Second cleavage. C. Resulting stage, each cell bi-nuoleate. //. Separation of the cells; 

 one of the nuclei in each enlarging to form the permanent nucleus, the other (probably repre- 

 senting a polar body) degenerating. 



