240 On the Coloration of Marine Animals. 
the porpoises, and some, like the killer, are boldly blotched 
with white, as also is the arctic seal. Moreover, the hump- 
backed whale (IJ/egaptera longimana) has pure white flippers 
12 feet long, whilst the smaller rorqual has a bold white 
band across the flipper. The well-known Beluga is dull 
whitish all over. As all cetaceans come to the surface to 
breathe, they must frequently expose a black or brownish- 
black surface. Now black is a tint which is conspicuous in 
the sea, and accordingly the fishermen use black flags in 
preference to white on their dandys, since they are so easily 
recognized in the darkness or dull light of the early morning. 
That black should be a protection to these animals, and that 
species are whitish all over or have pure white flippers or 
bands, is a condition of things creative of uncertainty in 
regard to the theories alluded to. The bold white touches, 
for example, of the killer can scarcely be held to be recog- 
nition-markings, like the white tail of the rabbit. The 
variegated hues of the arctic seal may subserve protection. 
If they do, those of other colours are at a disadvantage. 
Considerable variety, indeed, occurs in the group; thus the 
elephant-seal is dull greyish above, light beneath, and the 
sea-leopard is spotted yellowish white and dark grey on the 
back, with a yellowish under surface. ‘The sirenians are dull 
brownish dorsally and ventrally, so that the lighter hue seen 
against the sky is absent in their case; but, on the other 
hand, they are not oceanic. 
A general survey of the coloration of marine animals raises 
doubts as to the interpretations which have been brought 
forward to explain it. Some of these explanations, it is true, 
are more or less in agreement with facts; but, so far as can 
be seen, other facts are adverse, and demonstrate the extreme 
caution necessary in dealing with such interpretations. 
Before anything definite can be produced a much more exten- 
sive, more exact, and long-continued series of observations 
on the subject is imperative. That the coloration, often so 
varied and so beautiful, is of importance to marine animals 
can scarcely be doubted, for Nature is ever prescient; but it 
is not always easy to adapt the theories of the day to her » 
workings. 
