CHROMATOLOGICAL RELATIONS OF SPONGILLA FLUVIATILIS. 51 
the blue chlorophyll. The result of these changes is that at 
one particular state of partial development the ratio between 
the blue and yellow chlorophyll and that between all the 
different yellow constituents are the same in the leaves of the 
highest plants as in the well-developed Spongilla, but even 
then there is not perfect agreement, since it contains a far 
greater amount of the chlorophyll in relation to the other 
constituents. Comparing together different portions of the 
Spongilla in the same manner, we arrive at similar results. 
The lower portions, where exposed to feeble light, are far yel- 
lower than the exterior, and contain relatively much less 
chlorophyll, and the proportion between the yellow and blue 
chlorophyll is even less than normal. ‘There is also a rela- 
tively less amount of orange xanthophyll, but an increased 
quantity of lichnoxanthine and of the yellow substance 
soluble in water which resembles that met with in fungi. It 
will thus be seen that the lower and less perfectly developed 
portions of the Spongilla approximate in these chromato- 
logical characters to the lowest type of normal lichens, and 
present us with a lower type of colouring than any that I 
have yet been able to find in the most rudimentary leaves of 
the higher classes of plants. 
Taking, then, all the above facts into consideration, it will 
be seen that the colouring of Spongilla is not exactly the same 
as that of any particular class of plants, but represents more ° 
or less closely a special low type, in which development has 
proceeded according to a somewhat different law up to a 
point reached at an early period of their growth by the leaves 
of the highest classes of plants. The analogy between these 
facts and those met with in structural embryology will not 
fail to strike every one, and | cannot but think that the further 
study of such questions will throw much light on many in- 
teresting problems. 
Seeing also that the less developed portions of Spongilla 
lose more and more of the characters of the higher plants 
and approximate more to the type of fungi, one need not be 
so much surprised that in some species of sponge the plant- 
character is altogether lost, and that the type of colouring 
closely approximates to that of fungi and of the lower 
animals. It would, I think, be therefore well worthy of study 
to ascertain whether low animal forms which, like Spongilla, 
contain chlorophyll, have when exposed to light the power 
of decomposing carbonic acid and supporting themselves to 
some extent as plants, and at the same time have the power of 
supporting themselves by meaus of organic particles conveyed 
