450 



Mr. P. Geddes. Observations on the 



[Mar. 27, 



with starch, though of widely different properties, his paramylon ; * 

 but these facts seemed as much to point towards the algoid nature of 

 these long disputed organisms f as to warrant our supposing a more or 

 less vegetable mode of life in animals so well organised, and so evidently 

 carnivorous as Coelenterates and Turbellarians, especially as the only 

 recorded experiment, that of Max Schultze % on Vortex viridis, yielded a 

 totally negative result. Some such hypothesis, however, can hardly 

 help recurring to the observer of the light-seeking habit of Hydra 

 viridis, 



Last spring, when at the Laboratoire de Zoologie Experimentale of 

 M. de Lacaze-Duthiers, at Roscoff, I was much interested by the green 

 Rhabdoccele Planarian,§ Gonvoluta Schultzii, 0. Schm., crowds of 

 which, lying at the bottom of the shallow pools left by the retreat- 

 ing tide, resembled at first sight patches of green filamentous algee. 

 Their abundance in fine weather on the surface of the white sand, 

 covered only by an inch or two of water apparently to bask in the sun, 

 was very striking, at once suggesting that their chlorophyll thus so 

 favourably situated must have its ordinary vegetable functions. I 

 accordingly returned to Roscoff in the autumn to make experiments. 



The mode of procedure was evidently to expose the Planarians to 

 sunlight to observe whether any gas was evolved, and if so to analyse 

 it qualitatively and quantitatively. After one or two trials a form of 

 apparatus — the simplest possible — was found, which answered admir- 

 ably. It merely consisted of a couple of the round shallow glass 

 dishes used in the laboratory as small aquaria, the edge of one fitting 

 as nearly as possible, when inverted, into the bottom of the other. 

 Into the larger vessel were put Planarians enough to cover the bottom ; 

 it was then gently sunk in the pneumatic trough (a tub of sea water), 

 and the smaller, also full, inverted into it. The apparatus was then 

 placed on a shelf in the sunshine, and left to itself. The movements of 

 the animals were greatly accelerated by the exposure, and in a quarter 

 of an hour minute bubbles of gas were to be seen in the film of mucus 

 plentifully secreted by the Planarians. These bubbles rapidly increased 

 in number and volume until they buoyed up the whole sheet of mucus 

 with its entangled Planarians and grains of sand to the top of the 

 water in the inverted dish. Here the evolution of gas continued more 

 actively than ever, until the animals had disengaged themselves and 

 descended to the bottom, there to recommence as before, the mucus 

 meanwhile dissolving and allowing the bubbles freely to unite. Thus 

 the first half of the inquiry was answered in the affirmative, 



* G-omp Besanez, " Traite d' Analyse Zoochimique," p. 127. 



f JEuglena is claimed by both Sachs and Claus in their manuals of Botany and 

 Zoology respectively. 



% " Beitrage zur JSTaturgeschichte der Tnrbellarien." 

 § " Neue Bhabdocoelen." Wiener Sitzungsb., 1852. 



