232 



GENERAL PHYSIOLOGY 





upward obliquely at a certain angle. The Closkrmm shoves itself 

 slowly forward, as Klebs ('85) and Aderhold ('88) have shown, 

 by the attached end expelling a mass of slimy secretion (Fig. 93), 

 the cell maintaining approximately its angle of inclination to the 

 bottom. But in gliding forward it alternates its two poles, the 

 swinging pole sinking, adhering and secreting, while the previously 

 attached pole rises and swings freely. Thus the alga gradually 

 moves forward upon its support. 



As regards the movement of the Diatomcm. the small, brown, 

 boa -shaped or rod-shaped Algce, provided with an extremely 



delicate silicious shell, which are found 

 in enormous variety in both fresh and 

 salt water, a literature almost too 

 ■i; vast for review has appeared. When 



V these unicellular forms are observed 



■:;. in a drop of water upon a slide, they 



;;.i are seen gliding forward upon the 



bottom in the direction of their long 

 axis in a peculiar hesitating manner, 

 sometimes slowly, sometimes rapidly, 

 and often going backward with the 

 poles reversed in direction. It seems 

 impossible to discover any sort of 

 locomotor organs in the body. The 

 numerous investigators who, like Max 

 Schultze, Engelmann, and others, 

 earlier studied this graceful form of 

 motion, adopted widely different views 

 as to its origin. Afterward, from the 

 researches of Biitschli ('92, 2) and 

 Lauterborn ('94), it appeared as if it 

 depended upon the above principle of 

 the extrusion of a slimy secretion. 

 Biitschli and Lauterborn succeeded 

 in showing that certain forms of 

 Diatomem are enveloped in a covering of jelly and extrude 

 peculiar threads of secretion, which can be made visible by 

 adherent granules of india ink (Fig. 94). But recently the very 

 detailed investigations of O. Miiller ('93, '94, '96, '97) have 

 shown that these threads have a subordinate significance in the 

 progression of the DiatomecB, and that the mode of motion of these 

 small cells is much more complicated, and perhaps more allied to 

 movement by protoplasmic streaming. 



As to the long, blue-green, thread-like Oscillarim, which consist 

 of many cells arranged one after another in a row and creep slowly 

 through the water like the Diatomecc, it is highly probable that 

 they really shove themselves along the bottom by the expulsion of 





Pig. 94. — Diatom with threads of slime 

 extruded. (After Biitschli.) 



