14 INTRODUCTION. 



The organization the most simple, is that which is found 

 in the Conferva; ; and I have reason to think that it repre- 

 sents a type general to the spores of the Alga. I have 

 studied it in the Conferva glomerata and C. rivularis ; the 

 spores are altogether alike in both species, and I have seen 

 in the one all that I have observed in the other. Their 

 form is turbinated; the thin extremity, deprived of endo- 

 chrome, to which the name of rostrum or beak has been 

 given, bears two cilia or filiform tentacles, the length of 

 which surpasses that of the spores ; they are the locomotive 

 organs. (See Plate I. Jig. 1, 2.) The spore moves ordinarily 

 with the beak in advance, and turns about in the water with 

 a movement of trepidation, which recalls to mind that which 

 I have observed in the animalcules of the anther of Chara : 

 this analogy applies itself more closely from the resemblance 

 of the organs of locomotion. From time to time the spore 

 suddenly stops ; and often, likewise, it twirls round upon its 

 great axis. The light exerts a marked influence upon the 

 direction of its march. A small quantity of the watery 

 extract of opium is sufficient to arrest their movements. 

 The tentacles are then easily distinguished by a linear power 

 of 240 times (la vue moyenne etant comptde a 25 centi- 

 metres). They are rendered still more visible by employing 

 the alcoholic tincture of iodine, more or less weak. If after- 

 wards the spores are left to dry between two plates of glass, 

 the tentacles will not be observed to be altered by the 

 drying, but they come in a manner more satisfactory and 

 positive upon the bottom of the microscope, because they 

 are placed in a medium less refracting. It is necessary to 

 remark, moreover, (and this observation applies to all spores 

 of the Alga which are prepared in this manner,) that, the 

 spore contracting itself by drying, the tentacles appear a 

 little longer. 



It is in the morning more particularly that the greatest 

 number of spores of Conferva are found in action. Those 

 which one observes after mid-day are for the most part 

 stopped, or have already commenced to germinate. The mo- 

 tionless spores all present, towards the beak, a point coloured 



