9f 



and DIG3Y, fO?) . 



In thallophytes, the evidence at hand indicates great 

 diversity in the point at which the numerical reduction of 

 cliroino somes takes place. Even in the single group of Rho- 

 dophyceae, the point of reduction occurs at different 

 places in the life history of different species. When one 

 comes, therefore, to regard the chromosome n\jjnl3er as the 

 sole test for the delimitation of sporophyte and gameto- 

 phyte, it seems prooaole that confusion vdll result. V'ith 

 this in mind, I shall now reviev/ briefly the opinions ex- 

 pressed by workers in tJiis field as to the alternation of 

 generations in the red algae; and shall venture to offer 

 some suggestions as to the meaning of the rather compli- 

 cated nuclear life histories of members of this group, 



OLTrJ^TlTS. {*9Q) after a careful study of the develop- 

 ment of the cystocarp in four genera, came to the conclu- 

 sion that the sporogenous cells constitute a generation 

 similar to the sporophyte of the Archegoniate series. La- 

 ter, ('05, '07) he elaborated this conception and expressed 

 the opinion that the sporophyte is of antithetic origin, 

 i.e., that it became gradually intercalated in the life his- 

 tory by b. series of stages of increasing cojnplexity. In 

 those forms in v/hich the tetraspores are borne on distinct 



