Cytology and Movements of the Cyanophycea. 317 



on the different sides." In order to account for the rapidity 

 of this motion being greater than could possibly be caused 

 by the one-sided splitting of the cells of the trichome, Stras- 

 burger continued, ''These flexions usually take place slowly, 

 but can, however, induce violent movements when the flex- 

 ion is stopped by some obstacle, and then by overcoming 

 this the tension is suddenly equalized. The movements can 

 only take place when the threads have a point of support on 

 some other object." This last statement is contrary to the 

 observations of Engelmann, as well as my own, as will be 

 shown later. The evidence of nearly all observers on the 

 hormogonia would also militate against it. 



The observations of Schultz and his followers seem much 

 more to the point. Such movements occur nowhere else 

 among living organisms without the presence of some kind 

 of locomotory apparatus, usually cilia in some form. In 

 the light of the facts above stated, it would seem, therefore, 

 that we have only two methods left as plausible explana- 

 tions of the motions of the Cyanophyceae, i. e., either (a) a 

 protoplasmic pellicle which creeps along on a substratum 

 and which acts in a peristaltic manner, or (&) the plant has 

 some propelling organ as flagella or cilia or pseudopodia, 

 that act either upon the solid substratum or that move freely 

 through the water. The former of these theories could 

 scarcely account for all of the activities, though it might 

 assist in them. While studying the species of Oscillaria, I 

 was convinced that there was, at times, a very delicate pel- 

 licle surrounding the trichomes. This pellicle, as is shown 

 above, would take a delicate tint with protoplasmic stains. 

 On several occasions I saw a lengthening and shortening 

 of the cells as in peristaltic movement, but it was by no 

 means sufficient to cause the oscillation and especially the 

 creeping movements of the organism. Neither was there 

 any observed evidence that the peristaltic movements, if 

 such they could be called, were caused by the surrounding 

 delicately staining sheath, even though it should prove to 



