EDWARD S. CASTLF.. 



the two months it was under observation, nevertheless was 

 judged an Anabcena on its general morphology. Exact determi- 

 nation of the species was not attempted by the writer but will 

 be referred later to specialists in the classification of the group. 



10 



FIG. I. Portions of the trichomes of the motile species of Anabcena studied at 

 Soledad. (a) The smaller species showing its characteristic structure, (b) The 

 larger species showing the cells, heterocyst, and spore in their characteristic 

 arrangement. 



Both these species of Anabcena were consistently and actively 

 motile, the motility resembling in general that customary in the 

 Oscillatoriacea*. Flexion of the w r hole filament as well as 

 translatory movement was seen in both species, but rotation 

 was not observed. Filaments with heterocysts moved as actively 

 as those without, contrary to what Borzi (1886) observed in the 

 case of species of Nostoc. Speed of translation was, within 

 limits, independent of the length of the filament, confirming the 

 observations of Crozier and Federighi (1924) on Oscillatoria. At 

 28.9 C. (84 F.), the rates of translation of these species of 

 Anabcena, compared with the rates of some rapidly-motile species 

 of Oscillatoria, were: 



Anabxna sp. . . . av. 2.5 M per sec. 



Oscillatoria formosa ... 4.2 n 



Oscillatoria princeps 5.0 ^ 



The rate of movement in Anabxna is thus seen to be half 

 that of Oscillatoria princeps and somewhat more than half that 

 of Oscillatoria formosa under the same conditions. Although 

 motility has not been reported in Anal>;nia hitherto, the motility 

 which has been recorded frequently in the hormogonia or such 

 related Heterocystere as Nostoc, Scytonema, or Rivitlarin has in- 



