THJ-: NATTRK OF DIATOM MOTION. 121 



ronmeiital influences. Moreover, here is the straight gate 

 wherethrough comes into the world the power of motion in 

 living things both great and small. But while this " chloro- 

 phyll reaction " is thus at the bottom of all motion, and a 

 condition precedent thereto, it is not the effect, or the symp- 

 tom, or the chemical outcome of any protoplasmic effort 

 whatever. The symptom, the result and the chemical accom- 

 paniment of protoplasmic work, such as is typified by mus- 

 cular labor, is the absorption, the disappearance of ox3^gen, 

 as such, and the expulsion of carbon dioxide. To perform 

 work the organism must have oxygen, and in performing work 

 it gives off carbon dioxide. 



Now this is the question : Does the diatom, require oxygen 

 in order to move, and does it, as a result of its motion, give 

 off carbon dioxide ? 



I have had occasion to state * that whilst in a case espe- 

 cially studied, filamentous and vegetative diatoms enclosed in 

 glass tubes with water slightly tinted with hsematoxylin and 

 partly saturated with carbon dioxide, did, in short order, 

 under the influence of bright sunlight, absorb much carbon 

 dioxide and generate much oxygen ; the same diatoms, 

 possibly stimulated into the motile condition by the oxygen so 

 generated, expanding over the inner surfaces of the tubes and 

 continuing for hours in semi-darkness their lively motions, 

 reversed themselves and now gave out again large quantities 

 of carbon dioxide, so that the deep-red color of the oxidized 

 haematoxylin was altered to a yellowish brown. This result, 

 which was considered significant of the essential nature of 

 motile activity in the case of liunotia, was further fortified by 

 the observation of Miiller that motile diatoms came gradually 

 to rest under a cover glass in the absence of a sufficient supply 

 of oxygen, and that when oxygen was introduced anew the 

 motion was resumed. Miiller's statement, moreover, was later 

 confirmed by direct and repeated experiments on various 



*Proc. Acail. Nat. Sci., I'liila., iSg.S. 



