INTRODUCTION. 13 



have endeavoured to account for it by reference to the 

 principle t)f endosmosis ; but neither of these explanations 

 can be deemed satisfactory ; the true cause of it depending, 

 according to the researches of M. linger*, and M. Gustave 

 Thuretf, upon the presence of cilia, similar to those of the 

 infusory animalcules. The following abstract of M. Thuret's 

 paper, on a subject of such high interest, cannot fail of 

 being acceptable. 



The spontaneous movement of the spores of the Algaj 

 has been viewed by a great many observers. In certain 

 cases it is apparent to the unaided sight ; but until now, as 

 declares M. Dujardin, in his " Observateur, ou Microscope " 

 (Paris, 1843), they have not been able to discover by what 

 means the spores swim in the liquid. Nevertheless, the cilia, 

 or filiform tentacles, which serve them as locomotive organs, 

 do not appear to me more difficult to see. than the filaments 

 discovered by M. Dujardin in a great number of Infusoria ; 

 and if they have escaped an observer so practised, it is, 

 without doubt, because he has not continued his researches 

 with enough of perseverance, or else, that he has not made 

 them in all the conditions necessary for success. 



In fine, the movement of the spores continues for some 

 hours, during which the locomotive organs are in incessant 

 agitation, and in consequence very difficult to distinguish. 

 The use of coloured infusions cannot but detect their exist- 

 ence. When the spore stops, the locomotive organs dis- 

 appear very quickly, without leaving any traces, and some 

 time after, the germination commences. It is necessary 

 then to seize the precise instant when the spores cease to 

 move; or, to make the chances of success greater, it is 

 necessary, when one finds those which move with vivacity, 

 to put them in contact with a reagent the action of which is 

 too feeble to alter their form, but enough to stop their 

 movements. Opium and iodine appear to me the agents 

 the most proper to obtain this result. 



* Die Pflanze in Momente der Thierwerdung. Wien. 1843. 

 f Researches sur les Organes Locomoteurs des Spores des Algues. 

 Par M. Gastave Thuret. Ann. des Sciences Nat., Mai et Juin, 1843. 



