PERIODICITY IN SPIROGYRA. 55 



filaments 



period 



No. 5 of the second series began to twine around each 



themselves 



1 



of the eleventh series (.005% each of Na 2 HP0 4 and 

 NaH 2 P0 4 ) developed very marked false branches which did 

 not resemble conjugation tubes but were much larger and 

 longer. Several of the other cultures showed distortions of 



marked character but 



tion whatever. 



rred 



from time to time in verv different solutions but 



sufficient 



due 



an incomplete response to some stimulus to conjugation. A 

 number of similar experiments with this form need not be 

 considered beyond noting that Benecke's methods when tried 

 under various conditions uniformly failed to produce conju- 

 gation except in the single case to be described in the follow- 

 ing paragraph. 



April 29, a mass of S. longata was found conjugating. Fila- 

 ments that had already conjugated were pulled out from the 

 rest and the remaining material (A) was used to start four 

 cultures, two in No. 3 of Benecke's second series and two in 

 No. 4. One of each was placed in the laboratory, the others 

 in the brook. Four parallel cultures (B) were identical ex- 



material was from another mass 



found. May 10 the ma 



from 



more or less conjugation (but 



zygotes) in No. 4. These results approximate those of 

 Benecke, the only clear case so far as this species is concerned. 



showed 



most nart death 



good 



different condition in the laboratory. Although No. 4 in the 



tube 



develop and 



The 



bright light of a south window 



