474 



Mr. H. C. Sorby on 



[June 19, 





Olive. 



Ked. 



Green. 



~ni 11 l n 



Blue chlorophyll 



+ 



+ 











+ 



Chlorof ucine 



+ 



• 





Orange xanthophyll 





+ 





Xanthophyll 





+ 



+ 



Yellow xanthophyll 







+ 

















+ 







+ 





Pink phvcocyan 









Red phycoerythrine 









On inspecting this Table it will be seen that the olive Algce are charac- 

 terized by the relatively large amount of chlorofucine and fucoxanthine, 

 and the total absence of yellow chlorophyll, of xanthophyll, and of yellow 

 xanthophyll. The red are especially distinguished by the colouring-matters 

 of the phycocyan and phycoerythrine groups, but also differ from the olive 

 in containing xanthophyll and very little chlorofucine and fucoxanthine. 

 The green are characterized by the presence of yellow chlorophyll and 

 yellow xanthophyll, as well as by the absence of chlorofucine, fucoxanthine, 

 and the substances soluble in water, so characteristic of the red group. 

 Blue chlorophyll, orange xanthophyll, and the lichnoxanthines are com- 

 mon to all. It will also be seen that the red group is intermediate 

 between the olive and the green, and, independent of the red colouring- 

 matters, it differs from each of the other groups far less than they do 

 from one another. It is also still more closely connected with each by 

 other examples. My endeavour has been to extend such a method of 

 comparison to all the leading classes of plants and to some of the lower 

 classes of animals, and to ascertain the order in which they should be 

 arranged, so as, in like manner, to show the most gradual and unbroken 

 passage from one to the other. 



Connexion between the loiuest classes of Animals and Plants. 



Comparing these various groups of Algce with other classes of plants, 

 and with such low classes of animals as Actinias, I found that the whole 

 of the colouring-matters present in green Algce are those most characteristic 

 of all the higher plants, the only difference being that in certain circum- 

 stances these latter contain in addition various more or less accidental 

 and unessential substances, belonging to the erythrophyll and chryso- 

 tannin groups, some kinds of which, nevertheless, do to some extent appear 

 characteristic of particular classes. As far as their constituent colouring- 

 matters are concerned, the green Alga? are therefore perfectly typical 

 plants. On the contrary the olive Algce differ in a very marked manner ; 

 they contain no yellow chlorophyll, nor either of the two kinds of 



