sorby's researches on chromatology. 103 



which, nevertheless, do to some extent appear characteristic of par- 

 ticular classes. As far as their constituent colouring-matters are 

 concerned, the green Algce are therefore perfectly typical plants. 

 On the contrary the olive Algce differ h\ a very marked manner; 

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

 xanthophyll, all so characteristic of the most perfect plants, but 

 contain chlorofucine and fucoxanthine, both of which occur in cer- 

 tain species of Actinia?, like Anthea cereus, var. smaragdina. The 

 presence of such colouring-matters, therefore, connects the olive 

 Algce with the lower classes of animals, in the same manner that 

 the presence of blue chlorophyll connects some animals with plants. 

 Such substances, though essential to the growth of plants, arc not 

 constant in closely allied species of animals, as though they were 

 of no more importance for the life of animals than the accidental 

 vegetable colouring-matters are for the life of plants. The value 

 of these connexions between plants and animals remains to be de- 

 termined, but in any case such definite facts must, I think, have 

 some very important signification. If, then, according to these 

 principles, the olive Algce be looked upon as a link connecting the 

 lowest classes of plants with some of the lowest classes of animals, 

 there is a perfect and simple continuity ; whereas if they were to 

 be considered intermediate between green Algce and the higher 

 Cryptogamia, there would be two great breaks of chromatological 

 continuity. 



Changes occurring in Oscillatorice. 

 The olive Algce are also connected in another manner with lichens, 

 through Oscillatorice. These latter plants are extremely interest- 

 ing, since they are subject to most remarkable changes, depending 

 on the conditions in which they grow. I have made a series of 

 quantitative analyses, which show this in a striking manner. I 

 may here say that the chief difficulty in the analysis was the de- 

 termination of the amount of the lichnoxanthines in presence of 

 chlorofucine and fucoxanthine, and therefore the quantities given 

 must be looked upon as only approximate, derived from several 

 different methods, none of which were perfectly satisfactory, though 

 they all agreed in leading to the same general conclusions. In dis- 

 cussing the results of the analyses, it was requisite to take the 

 amount of blue chlorophyll as uniform, since it was the only con- 

 stituent occurring in any considerable quantity throughout the 

 v hole series. To have taken equal weights of the plants them- 

 selves would have been almost impossible, and would often have 

 made those which really correspond very closely appear to differ 

 extremely, since the constitution of the endochrome is the impor- 

 tant question. Of course by thus calculating the results as if the 

 amount of chlorophyll were the same in all, there appears to be an 

 increase in some of the other constituents in the specimens exposed 

 to the sun, due, however, in reality to a reduction in the relative 

 quantity of chlorophyll. 



