OBSERVATIONS ON MOTILITY IN CYANOI'I! VCI I 7 I 



variably been described as of a very slow nature. The rate- 

 given by West (1916, p. 23), as found by Brand for the hormogonia 

 of species of Phormidium, vary from 0.004 to 0.05^ ^ per second, 

 and are thus many times slower than those seen by the writer 

 in the vegetative filaments of Anabxna; but it should be noinl 

 that the temperature at which these slower rates occurred \\.i- 

 not given. 



In view of the fact that during the movement of these species 

 of Anabxna no rotation was ever observed by the writer, it 

 seemed advisable for comparison to examine species of Oscillatoria 

 in this respect, especially since Crozier and Federighi (loc. dt.) 

 have expressed some doubt whether rotation of the filaments of 

 Oscillatoria does indeed always take place during translation. 

 Careful examination of a considerable number of favorable 

 species of Oscillatoria at Soledad has convinced the writer most 

 conclusively that .many species do exhibit rotation of the filament 

 around the long axis. In species in which the ends of the fila- 

 ments were characteristically hooked, this hook, which main- 

 tained its peculiar shape, could be seen to rotate through the 

 water in a manner precluding a mere circular bending of the tip. 

 Moreover, in larger species, rotation could be observed very 

 convincingly by following the change in relative position of 

 granules lying at different depths within the cell content. 



Also, in view of the fact that West (1916 and 1904), when dis- 

 cussing the motility of Arthrospira, states that rotation has not 

 been observed in this genus, it may be of interest to record that 

 in a species studied at Soledad, rotation was found to accompany 

 progression, as in Spinilina, while flexion also was seen to occur 



at times. 



SUMMARY. 



Two species of Anabxna, of the family Nostocacea, studied in 

 Cuba, were found to exhibit motion similar to that of the Oscil- 

 latoriaceee. The rate of movement was independent of the 

 presence of heterocysts or of the length of the filament, and was 

 about one half that of actively motile Oscillatoria? under the 

 same conditions, but much more rapid than that previmi>l> 

 recorded for the hormogonia of Phormidium. No rotation was 

 observed in these species of Anabxna but several species of 



