MOVEMENTS OF OSCTLLATOEIACE.E. 



323 



Fig. 149. 

 J3 



stitute the most remarkable feature in their history. These are 

 described by Dr. Harvey* as of three kinds ; first, a pendulum-like 

 movement from side to side, performed by one end, whilst the other 

 remains fixed so as to form a sort of pivot ; second, a movement of 

 flexure of the filament itself, the oscil- 

 lating extremity bending over first from 

 one side and then to the other, like the 

 head of a worm or caterpillar seeking 

 something on its line of march ; and 

 third, a simple onward movement of 

 progression. "The whole phenome- 

 non," continues Dr. H., "may perhaps 

 be resolved into a spiral onward move- 

 ment of the filament. If a piece of the 

 stratum of an Oscillaioria be placed in 

 a vessel of water, and allowed to re- 

 main there for some hours, its edge 

 will first become fringed with filaments, 

 radiating as from a central point, with 

 their tips outwards. These filaments, 

 by their constant oscillatory movements, 

 are continually loosened from their 

 hold on the stratum, cast into the 

 water, and at the same time propelled 

 forward ; and as the oscillation con- 

 tinues after the filament has left its nest, 

 the little swimmer gradually moves along, 

 till it not only reaches the edge of the 

 vessel, but often — as if in the attempt to 

 escape confinement — continues its voyage 

 up the sides, till it is stopped by dryness. 

 Thus in a very short time a small piece 

 of Oscillatoria will spread itself over 

 a large vessel of water." This rhythmi- 

 cal movement, impelling the filaments 



in an undeviating onward course, is evidently of a nature alto- 

 gether different from the truly spontaneous motions of Animals ; 

 and must be considered simply as the expression of certain vital 

 changes taking place in the interior of the cells. It is greatly 

 influenced by temperature and light, being much more active in 

 warmth and sunshine than in cold and shade ; and it is checked by 

 any strong chemical agents. — The true Generation of Oscillatoriacece 

 is as yet completely unknown ; and it does not seem at all unlikely 

 that these plants may (like the Nostochacece, § 244) be the 

 1 motile ' forms of some others, probably Lichens, which in their 

 • stiil ' condition present an aspect altogether different. 



W. 



Sti-ucture of Oscillatoric. 

 eontexta ; — a, portion of a 

 filament, showing the stria- 

 tions on the cellulose coat, 

 a, a, where the endochrome 

 is wanting; b, portion of 

 filament treated with weak 

 syrup, showing a disposition 

 to a regular breaking-up of 

 the endochrome into mas- 

 ses ; c, portion of filament 

 treated with strong solution 

 of chloride of calcium, show- 

 ing a more advanced stage 

 of the same separation. 



" Manual of British Marine Algse," p. 220. 



T 2 



