312 Phillips on a Comparative Study of the 



forward are produced by diosmotic processes in consequence 

 of which the turgor becomes greater in the cells of one end 

 of the filament than in the cells of the opposite end. As 

 long as the turgor remains in this one-sided condition, the 

 filaments move forward in one direction, when, however, by 

 an influence {e. g., the friction of the foundation) the 

 turgor of one of these cells grows less, that of the other end 

 increases and the movement is reversed." Those specimens 

 which grew on the surface of the soil or other substratum 

 were always surrounded by a delicate pellicle of water in 

 which they moved by means of these same osmotic currents. 

 In addition to these currents he thought the contractility of 

 the protoplasts of the cells also assisted in causing motion 

 though this had not been shown directly. 



Engelmann (22) saw in OsciUaria the inconceivably deli- 

 cate slime pellicle of von Siebold and others surrounding 

 the whole trichome, but interpreted it as a protoplasmic layer 

 which by unequal contraction caused a peristaltic move- 

 ment of expansion and contraction. This he thought was 

 what caused the creeping movement of OsciUaria. When 

 in contact with some supporting substance, inconceivably 

 delicate as this protoplasmic envelope was, nevertheless it 

 could raise an object of over one thousand times the weight 

 of the trichome. He separated the oscillatory and spiral- 

 like movements from the creeping motion. The former were 

 almost exclusively seen when OsciUaria was free-swimming 

 and did not need any supporting substance. He said : 

 "Their absolute speed is much more definite than in any 

 known case of protoplasmic motion. Without doubt they, 

 the motions, are brought about as in the case of related bac- 

 teria, by glittering hairs, which are closely akin to whips. 

 In some forms these flagella are seen. There is known no 

 other source of similar expression of strength in the animal 

 realm, and it is sufficient for a complete expression of all the 

 facts." 



It is regrettable that Engelmann has left no figures to 



