384 Proceedings of the Royal Society 
an analysis, while the larger and finer smaragdina had scarcely 
produced a bubble. Two varieties of Ceriactis aurantiaca, one 
with, the other without, yellow cells, were next exposed, with a 
precisely similar result. The complete dependence of the evolution 
of oxygen upon the presence of algae, and its complete independence 
of the pigment proper to the animal was still farther demonstrated 
by exposing as many as possible of those known to contain yellow 
cells (Aiptasia chamceleon , Helianthus troglodytes , &c.), side by side 
with a large number of forms from which these are absent, such 
as the green Actinia carl , Actinia mesembryantliemum, Sagartia 
parasitica, Ceriantlius , &c. The former never failed to yield 
abundant gas rich in oxygen, while in the latter series not a single 
bubble ever appeared. 
Thus, then, the colouring matter of Anthea, described as chloro- 
phyll by Lankester, has really been mainly derived from that of the 
endodennal algse of the variety plumosa, which predominates at 
ISTaples, while the Anthea-green of Krukenberg must mainly consist 
of the green pigment of the ectoderm, since the Trieste variety evi- 
dently does not contain algae in any great quantity. But since the 
Naples variety, contrary to the opinion of the brothers Hertwig,* 
does contain a certain amount of ordinary green pigment, and since 
the Trieste variety is tolerably sure to contain some algae, Heider 
having indeed shown the presence of yellow cells in Sagartia, both 
spectroscopists have thus been operating on a mixture of two wholly 
distinct pigments — one vegetable, the other animal — diatom-yellow 
and Anthea-green. 
But what is the physiological relationship of the plants and 
animal thus so curiously and so intimately associated ? Everyone 
knows that the colourless cells of a plant share the starch formed by 
the green cells, and, in fact, subsist at their expense, and it seems 
impossible to doubt that the animal cell must similarly profit by its 
labours. In other words, when the vegetable cell dissolves its own 
starch, some must needs pass out by osmosis into the closely 
enveloping protoplasm of the surrounding animal cell, nor must it 
be forgotten that the latter possesses abundance of amylolytic 
ferment. Then, too, the Philozoon is subservient in another way 
to the nutritive functions of the animal, for it dies and is 
* Cf., Hseckel, Jena Zeitsclir ., 1870, p. 532. 
