INTRODUCTION. 17 



portion which quickly increases in volume, BO that the opposite 

 extremity becomes separated from the filament. At the same 

 time the spore commences to turn on its great axis in such a 

 manner, as that all the granules which it contains are seen to 

 pass rapidly from right to left, and from left to right, as 

 though they moved in the interior of a transparent cylinder. 

 The operation by which the spore endeavours to escape 

 occasions a very marked contraction ; but in some few 

 instances it succeeds in disengaging itself, and springs with 

 rapidity into the surrounding liquid. The colourless part, 

 which corresponds to the beak, is always directed in advance. 

 The spore does not cease to turn upon itself, but its progress 

 is somewhat regular, quicker or slower in one direction or 

 another ; in general, it quickly reaches the edge of the glass as 

 though it tried to escape ; sometimes it stops ; then in an 

 instant afterwards it resumes its course. The epispore from 

 which the cilia proceed describes a large granular areola. 

 As to the cilia themselves, they are invisible by reason of the 

 rapidity of their movement ; but we may judge well of their 

 action by putting the spore in an infusion of carmine, indigo, 

 or gum water, &c. Nothing is more curious than to follow 

 its progress in a strong infusion of carmine for example. 

 The coloured granules through which the spore makes its way 

 are driven with force by the motion of the cilia; a rapid 

 current is established on each side of the spore, and a long 

 track is described after it. When it meets with an obstacle, 

 such as the filaments of Zygnema or Vaucheria, it becomes 

 deformed (or is put out of proportion) ; but the motion of the 

 cilia is not arrested. It is also the same when it is com- 

 pressed even to the extent of producing the extravasation of 

 the endochrome ; the vibration of the cilia continues in the 

 part not injured. I have observed many times the emission 

 of the spore in a coloured infusion, and then noticed that the 

 agitation of the granules by the motion of the cilia is not 

 felt until about a fourth part of the spore has been released. 



It is necessary, in order the better to see the cilia, to 

 arrest them by means of some reagent, such as opium, iodine, 

 the proto-nitrate of mercury, &c. The effects of the watery 



c 



