Miscellaneous. 223 



odour, which reminded me of that of the iSuberites upon the beach 

 at Banyuls. 



To sum up, the Convoliita, by the absence of the digestive tube, 

 the oesophagus, and even the mouth, by the activity of its ciliary 

 movements, and by the layer of chlorophyll- cells, has the api)ear- 

 ance of a physiological association, a symbiosis between a unicellular 

 alga and an acoelate worm. 



Thanks to the presence of the chlorophyllian element, the animal 

 can live in a medium deprived of air, in stagnant pools where life 

 would be impossible, while, by its vibratile movements, it con- 

 stantly furnishes the j^laut with the current of carbonic acid neces- 

 sary for its nutrition, and of which, in its turn, it utilizes the 

 oxygen originating from the chlorophyllian function. 



The physiology of Vonvolnta is necessarily reduced to endosmotic 

 exchanges, through the external cuticular layer, of liquid nutritive 

 substances and gaseous solutions. 



The act of respiration has been the subject of a full investiga- 

 tion made with much care by Mr. Patrick Geddes *. However, 

 being governed by ideas which are still current in vegetable physio- 

 logy, he has sought to collect and analyze the gases which seemed 

 to him to be evolved from these little organisms under the action of 

 the sun ; and, further, his researches were made upon a quantity 

 of animals so considerable (a surface of one third of a square metre 

 covered with Planarians) that it is impossible to draw deductions 

 from them as to the individual life of each. 



The first fact that strikes the observer after placing a certain 

 number of the Convolata in a series of flasks is the tendency that 

 they have to move towards that part of the room, or rather of the 

 flask, which is most strongly illuminated. It is an orr/anic j^lioto- 

 meter of extreme sensibility. 



These worms are destitute of visual organs, even rudimentary ; 

 but if it is true that vision in the higher animals is only the result 

 of chemical action, a decomposition of the retinic purple, we may 

 assume that the action of the chlorophyll iipon carbonic acid pro- 

 duces a sort of visual sensation in the animal. It is to be remarked 

 that the ascent of the Planarian takes place slowly, and, so to speak, 

 unconsciously, uiKler the influence of movements of the vibratile 

 cilia more energetic in the direction of the light. On arriving at 

 the surface of the water our worms attach themselves by their poste- 

 rior part ; but at the least agitation of the water or the vessel they 

 detach themselves and fall to the bottom with very precipitate 

 movements. 



As regards the emission of gases and the deductions that can be 

 drawn from them to furnish evidence, or the measure, of the respira- 

 tory act, I can assert that it does not exist. We have only to avail 



• Arch. Zool. Exp. torn. viii. 1879-80, 



