OF MICRO-ORGANISMS. 27 



element. This is not at all differentiated, but remains 

 diffused, like the whole nervous system. M. Pouchet 

 calls attention to the interest which his observation 

 affords from a taxonomic point of view. The Peri- 

 dinia have sometimes been classed among the vege- 

 tables; the presence of starch and of cellulose in their 

 protoplasm has induced Warming to classify them 

 among the Diatomaceae and Desmidiaceae. It is ad- 

 mitted to-day that certain Peridinia possess an eye, 

 an organ which has hitherto been considered as the 

 exclusive attribute of animals. Nothing more clearly 

 emphasizes the altogether artificial character of the 

 distinction between animals and vegetables than the 

 results of dealing with Micro-organisms. 



Before leaving the Peridinia, we would remark 

 that these small beings afford an interesting fact from 

 the point of view of the history of the Protozoa; they 

 are provided with a long flagellum; they exhibit in ad- 

 dition an equatorial line on which formerly a crown 

 of vibratile cilia was thought to be recognizable: this 

 supposed co- existence of a flagellum and of cilia had 

 determined the naturalists to form a group of Cilio- 

 flagellates, serving as a transition between the Fla- 

 gellates, properly so-called, and the Ciliates. Since 

 then it has been discovered that the Peridinia do not 

 possess vibratile cilia; what had given rise to this er- 

 ror is the presence of a second flagellum on the level 

 of the transverse line which we have just described; 

 the movements of this flagellum have the appearance 

 of vibratile cilia in motion. 



Some time before the investigations of M. Pouchet, 

 M. Kimstler (of Bordeaux) had discovered, in a Fla- 

 gellate of the genus Phacus, a red eye which is also 

 formed ^{ two parts; it is composed of a homogenous 



