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THE AMERICAN NATURALIST [Vol. XLIV 



fuses with the egg nucleus. These two asters es- 

 tablish the spindle poles of the first mitosis, which pre- 

 sents sixty-four chromosomes. The chromatin of the two 

 gametes is indistinguishable in the fusion nucleus. 



The interpretation of the life history of Fucus with its 

 phase of chromosome reduction so close to the differen- 

 tiation of the gametes involves great difficulties. Stras- 

 burger has long held the thallus of this plant to be a sporo- 

 phyte generation, assuming that the gametophyte phase 

 is represented by the third mitosis in the oogonium and 

 the few antheridial mitoses which follow the reduction 

 division. He would then regard the antheridia and 

 oogonia to be derived not from primitive sexual organs, 

 but from sporangia corresponding to the tetrasporangia 

 of Dictyota. This view involves a reversal of the rela- 

 tions between the gametophyte and sporophyte genera- 

 tions usual among the algre, since it supposes the almost 

 complete suppression of the gametophyte. However in- 

 teresting and suggestive is this interpretation, it can 

 hardly be considered other than a speculation until we 

 know more of the probable phylogeny of the Fucales. 



It has been evident for a number of years that the 

 life history of the Outleriaeea- probably involved 

 two phases represented by sexual and asexual plants, 

 respectively, and there has accumulated much evi- 

 dence from the studies of Reinke, Falkenberg, Sau- 

 vageau, Church and others indicating that these 

 phases present a true alternation of generations. The 

 forms most studied have been Cutleria multifida 

 with a large much branched thallus which develops 

 gametes, and Aglaozoma reptans, a small crustaceous 

 alga which reproduces by zoospores. On the germination 

 of the zygotes and zoospores of these types forms are 

 produced which very shortly take on vegetative char- 

 acters not of the parent plants, but from the zygotes 

 arise Aglaozo>na-\\kv sporelings and from the zoospores 

 sporelLngs totally unlike Aglaozoma, but with characteris- 

 tics of Cutleria. CJpou this behavior chiefly have been 



