Coloration of Marine Animals. 235 
be a warning colour, as Mr. Garstang supposes, for some 
fishes eat them. The tadpoles of such forms as Stye/a are 
pink, Clavelina shows bright orange and yellow, and bright 
green characterizes A. intestinal in tangle-roots and similar 
places between tide-marks, and A. depressa under stones in 
rock-pools. If the red hue of some Ascidians, e. g. A. scabra, 
is assumed to be a warning colour, what is to be said about 
such as Molgula, a colourless form, invested by a thick layer 
of gravelly mud or sand ? 
Is the dull red of Styela grossularia, projecting here and 
there through a layer of Halichondria panicea on the roofs of 
sheltered caverns, in the same category in regard to warning 
coloration as Ascidia scabra on the floating blades of the 
tangles ? 
The pelagic Appendicularians and their houses are generally 
translucent, but some are pinkish. ‘Their vast numbers, 
however, are little in need of protection. 
The Compound Ascidians, such as Botryllus, Botrylloides, 
Leptoclinum, and Aplidium, are often strikingly coloured, 
such as the yellow stars of Botryllus Schlosseri, the white 
surface of Leptoclinum durum, or the cinnabar colour of 
others; yet this does not appear, so far as observations go, to 
be either for protection or warning. Fishes bite off the sea- 
weeds on which some grow and swallow them. 
Certain Cyclostomes, like Myaine, living in mud are of a 
flesh tint or purplish, as in #dellostoma, while the river- 
lamprey is olive and the marine boldly mottled with bluish 
erey and black. Myaine has no warning tint, yet its abun- 
dant mucus is most offensive. 
Amongst Fishes the bony forms (Teleostei) are, on the 
whole, the most brightly coloured, the Klasmobranchs being 
more soberly tinted. In some bony fishes both sexes are 
brilliantly coloured, in others only the male. One general 
rule, with a few exceptions, prevails throughout the series, 
viz. that the dorsum is dark and the under surface pale, 
apparently for protection, the explanation usually given being 
that, looked at from above, the dark dorsum renders the fish 
more or less obscure, whereas looked at from below the white 
or pale under surface is invisible against the sky. Yet 
Cotius scorpius in rock-pools occasionally has the head pale 
orange and the dorsum speckled with the same colour, 
and the skate has a grey under surface. Further, when the 
under surface is upturned, as in femora, it becomes dark, 
but no mention is made of the dorsum, which remains dark. 
It can hardly be supposed, however, that many species of 
skate have a white under surface for this purpose, though 
