318 



SCIENCE 



[N. S. Vol. XXXIX. No. 1000 



strated cytologically to the satisfaction of 

 many workers, there is no loss of identity 

 of the chromosomes in the sporophyte, then 

 there is no very significant fusion at any 

 point in the life cycle in consequence of the 

 sexual process. Members of the two sets 

 of chromosomes may be interchanged or 

 shuffled, probably at synapsis, and thus 

 new sets or combinations be formed in the 

 haploid nuclei at reduction. These new 

 combinations, however, are still made up of 

 the same discrete individual chromosomes. 



The essence of the sexual process then, 

 as far as yet morphologically demonstrated, 

 consists not of a real fusion, but merely of 

 a temporary association, followed by a re- 

 assortment at sporogenesis, of those ulti- 

 mate, inheritance-bearing units — the chro- 

 mosomes. 



Duncan S. Johnson 



Baltimore, Md. 



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