3IO Phillips on a Comparative Study of the 



motion in the diatom in its natural surroundings, or that 

 the intensity of the light would differ appreciably after pass- 

 ing a distance of half the length of a diatom, one can 

 scarcely see the relation of his observations to organisms 

 as they occur in nature. 



Borzi (6) concluded that in general the mechanism of 

 the movements of Oscillaria cannot be explained. "It only 

 takes place," he said, "in this organism when the plant is 

 not multiplying, and as soon as multiplication begins, the 

 filaments come to rest, and the sheath becomes much 

 thicker." He demonstrated a continuity of the protoplasm 

 from cell to cell through a pore in the transverse wall, and 

 this assisted the plant to correlate its movements. Neither 

 isolated cells nor any form of the Cyanophycese that have 

 heterocysts were capable of movement according to his 

 observations. He was also led back by the different move- 

 ments of Oscillaria, to accepting a helicoid movement of 

 the filament due to heat, light, etc. 



F. Cohn (15) considered that Oscillaria required a solid 

 substratum to glide over. Without this they could not move. 

 He based his conclusions upon their power to spread over 

 the sides of the glass vessel in which they were being culti- 

 vated, and even to rise above the surface of the water. He 

 never found Oscillaria filaments swimming freely in the 

 water. They generally used other filaments as supports 

 when they could not reach other substrata. "In Beggiatoa," 

 he said, "there are short waves of contraction which run 

 over the filaments, and set them in a kind of peristaltic 

 motion." These peristaltic contractions "are seen until they 

 cease by the death of the filament." This is quite similar 

 to what De Bary (20) has described for germinating Cylin- 

 drospermnm, while Zukal (loi) saw wrinkles on the sides 

 of Oscillaria as it swayed backwards and forwards. Cohn 

 then continued : "According to these observations it cannot 

 be doubted that within Beggiatoa and the Oscillariese in 

 general, there is a contractibility which is made manifest 



