232 - PROFESSOR E. RAYLANKESTER. W.:r,,-.Vfi*r 



the modifying effects of aci<ls in solution. The deep absorp- 

 tion band in the dark red, whicli is seen even in weak sohi- 

 tions of green colouring matters spoken of by other observers 

 as " chlorophyll " or " chlorophylloid substance/' is, accord- 

 ing to Sorby, present in a slightly varied position in the case 

 of blue chlorophyll, in that of yellow chlorophyll, and in 

 that of chlorofucine, and also in a totally distinct substance 

 called Bonelleine. Hence no very precise conclusion can be 

 based upon the occurrence alone of this strong absorption 

 band in the red (as, for instance, had been done by myself 

 in the case of Hydra, Bonellia, Idotea, and Cheetopyerus).^ 



Moreover, the fine red fluorescence which is seen in an 

 alcoholic solution of leaf green is exhibited, according to 

 Sorby, equally by blue and yellow chlorophyll and by 

 chlorofucine, and, as we now know, by Bonnelleine and by 

 Moseley's Pentacrinin, the red rays having, hov/ever, in each 

 case a different and characteristic refrangibility. 



Thus, it appears that the investigation of the claims of 

 any given greenish coloured pigment to be regarded as 

 " chlorophyll " is by no means a simple matter. Supposing 

 the pigment to be soluble in alcohol, we still have to ascer- 

 tain which of Sorby's three groups (chlorophylls, xantho- 

 phylls, lichnoxanthines) are present, and which of each of 

 the species distinguislied by him within those groups. 



In order to do this we have to rely on : 



1st. Variations in degree of solubility in such media as 

 alcohol, ether, benzine, carbon bisulphide. 



2nd. Absorption spectra of the series of solutions obtained. 



3rd. Fluorescence and spectrum of the fluorescent light of 

 such solutions. 



4th. Reactions of the solutions with acids, alkalies, and 

 oxidising and reducing agents, which give rise to new com- 

 pounds or change the spectra characteristically. 



There are, however, yet to be mentioned two categories of 

 phenomena in relation to the chlorophyll bodies of green 

 plants which comprise data of a nature to assist us in 

 judging of the similarity or dissimilarity of the green pig- 

 ments of animals compared with that of the chlorophyll 

 bodies. These are, firstly, the physiological activities asso- 

 ciated with the chlorophyll bodies of plants ; and, secondly, 

 the morphological features of these bodies. 



' It is, however, very probable that blue cliloropliyll and yellow 

 clilorophyll, as well as the xanthophylls and lichnoxanthiues, are successive 

 phi/siological stages of metamorphosis of one (colourless ?) original mother- 

 substance, since they appear always to be found associated with one 

 another. 



