72 THE INFLUENCE OF INANIMATE SUKRODNDINGS. 



without further proof assert the presence of chlorophyll in any 

 animal, even if we could prove the animal's direct dependence 

 on li^ht, or the similarity of the spectrum of the solution of the 

 green pigment with that of chlorophyll, or even a possible 

 agreement in the microscopic structure. Positive proof of its 

 existence can be derived only by evidence of the presence of all 

 the characteristic properties of true chlorophyll in the green 

 colouring matter of the animal. And it may at once be said 

 that the decomposition of carbonic acid by green-coloured 

 animals has never been proved by exact experiment.* 



FiG."17.' — Animals in which chlorophyll grains have been detected, a, SlentorviriclU', 

 h, Eiiglma viridis ; c, Vortex viridis. The first two are Infusoria, the last is a Tur- 

 bcUarian. 



The animals (fig. 17) in which it has been asserted that 

 chlorophyll is present, belong exclusively to the Invertebrata. 

 Among the Protozoa the following are the best known ; Euglena, 

 Stentor, many Eadiolaria and Spongilla; the green fresh-water 

 polyp Hydra among the Coelenterata, and a few TurbeUaria 

 among the worms. '^ 



The arguments for the statement that the green colour 

 of these creatures is actually due to chlorophyll are many and 



* Such a decomposition has been recently proved by the experi- 

 ments of Mr. Patrick Geddes on the green Tnrbellarian worm, Convo- 

 luta Sclitdtxix. — (Tbans.) 



