THE FILAMENTOUS INDIVIDUAL 55 



time a very long filament, showing gametes at varying 

 intervals, and suggesting perhaps that gamete-formation was 

 proceeding on no definite plan. Sooner or later the fila- 

 ment would get broken, and then there would be several 

 filaments, apparently Individuals, but really only parts of 

 one Individual. 



Were the intercalated series of Spirogyra produced as 

 lateral outgrowths or branches, then the plan of growth 

 would be like that of a racemose plant, and the primary 

 and secondary branches would end in gametes, and we 

 presume that there would be a progressive diminution in 



Fio. 7. — Release from proximal cell-arrest in a diagrammatic 

 filament. 



branch cell-content. But in Spirogyra the filament 

 " branches " are interposed in the line of the filament, and 

 the terminal nature of the gametes is not obvious. 



Now while this theory of the development of the Spirogyra 

 Individual receives support from the proximal " zooidal 

 arrest " in certain zooidal series of higher types, it is also 

 confirmed in a curious way by phenomena observed in 

 another unbranching filamentous Alga called i3Edogonium. 



JSdogontttm. 



In this Alga, whose general characters are those of Spiro- 

 gyra, there are certain cells provided with what are known as 



