2 1 4 OSCILLA TORI^E. PAKT n. 



glass till arrested by the dry part above. 7 During- these 

 motions there is a corresponding alteration in the form 

 of the filamental tubes believed to arise from rhythmi- 

 cal periods of vital contractibility, which are affected by 

 light and heat, because the motions are more rapid in 

 sunshine than in shade; besides, they are checked by 

 strong chemical agents. Some of the species have a 

 tuft of delicate cilia at the extremities of their filaments. 

 The free stratified bundles contain the simplest form 

 of the Oscillatorise. Each filament is a straight or 

 slightly curved chain of cells, full of coloured matter, 

 and enclosed in a common transparent colourless tube. 

 Multiplication takes place in these by division ; when 

 about to multiply, two adjacent coloured cells, or the 

 two halves of a divided cell, recede from one another, 

 and the outer tube contracts at the point of division, and 

 separates them into two distinctly new filaments. Some- 

 times the transparent outer tube does not yield, so that 

 the divided parts retain their places in the tube, which 

 dilates when these new parts are again divided. The 

 manner of division varies with the species, and the 

 generic characters of the Oscillatorise depend upon the 

 different conditions of the external tube, and the form 

 and arrangement of the coloured cells within it. The 

 tube often contracts to the finest point during division, 

 and frequently consists of distinct coats, the number of 

 which increases upwards, sometimes with such regularity 

 as to produce a beautiful streaked effect. Like their 

 allies, the Oscillatorise are reproduced by zoospores, 

 While these parts are growing, but especially during 

 their dissolution, the endochrome undergoes various 

 changes of colour, staining the water they die in, and 

 rendering it putrid ; some of the common kinds emit a 

 strong odour of sulphuretted hydrogen. 



7 These motions were discovered, and are described by Dr. Harvey, in his 

 * Manual of British Marine Algs&.' 



