COLOURING SUBSTANCES. 79 



held to indicate their essentially vegetable nature, and but for the recent 

 demonstration by Stein and the present author, of a well-developed oral 

 aperture and accompanying capacity to ingest solid food, would yet furnish 

 a solid argument in support of such interpretation. Between the green 

 colouring matter of an Euglena and that of a Palmellaceous plant or 

 protophyte, such as Protococcus, there would appear to be absolutely 

 no distinction, the same substances in both cases exhibiting, furthermore, 

 a tendency, at a certain epoch of their existence, to assume a more or 

 less conspicuous red or crimson tint. This last-named phenomenon is 

 especially characteristic of the type figured and described by Ehrenberg 

 under the title of Astasia (Euglena} sanguined, the rapid change of colour 

 from green to red in which has doubtless given rise in many instances 

 to the legendary accounts in rural districts of the conversion of standing 

 water into blood, and has even been suggested by Ehrenberg as yielding 

 an intelligible interpretation of that mysterious "turning of the waters 

 into blood," which distinguished the visitation of the first Egyptian 

 plague. Green colouring matter closely allied to, if not absolutely identical 

 with the chlorophyll of vegetable organisms, is found, though in a more 

 distinctly granular or less diffuse state, in many other infusorial groups. 

 Instances in this connection are afforded by various Peridinia, but espe- 

 cially by Paramecium chrysalis, in which the greater part of the chlorophyll- 

 like endoplasmic granules exhibit, as previously related, a characteristic 

 circulatory motion. In the green variety of Stentor polymorphic it has 

 been shown by Professor E. Ray Lankester that the absorption-bands 

 yielded on examination with the microspectroscope, correspond closely 

 with those given by the green colouring matter of Hydra viridis and 

 Spongilla, and indicate the presence of an essentially chlorophylloid body. 

 Various other species of Stentor are also remarkable for the brilliant 

 colouring of their inner parenchyma, the pigmentary matter being distri- 

 buted in a granular form throughout its substance, and exhibiting in some 

 cases, such as 5. castaneus, under a high magnifying power, two distinct and 

 easily recognized tints. The most anomalous hue yet recorded is, perhaps, 

 associated with Stentor cceruleus, in which the dispersed pigment-granules 

 are of a brilliant and intense blue. Submitted to spectroscopic analysis, the 

 absorption-bands yielded by the bodies of this species, either singly or en 

 masse, were found, by the author above quoted, to differ so remarkably 

 from those of any other known organic substance, that he has proposed to 

 distinguish it by the suggestive title of "stentorin." * 



In a number of animalcules, equalling if not exceeding what may be 

 termed the chlorophyllaceous series, the parenchyma is found to yield a 

 colouring matter mostly diffuse, as in the green colour of an Euglena 

 the fundamental hue of which is brown, but varies from pale amber or 

 orange to a deep olive. In this latter instance the aspect of the pigmentary 

 matter closely approaches that of " diatomin " or the essential olive-brown 



* "On Blue Stentorin," E. Ray Lankester, 'Quart. Journal Micro. Science,' April 1873. 



