ending in long tendrils, and useful for attaching them
to corallines or seaweeds on the bed of the ocean. But it is worth
noticing that in colour the egg-cases closely resemble the common wrack
to which they are oftenest fastened; and as they wave up and down in
the water with the dark mass around them, they must be almost
indistinguishable from the wrack itself by the keenest-sighted of their
enemies. This protective resemblance, coupled with the toughness and
slipperiness of their leathery envelope or egg-shell, renders them
almost perfectly secure from all evil-minded intruders. As a
consequence, the dog-fish lay but very few eggs each season, and those
few, large and well provided with nutriment for their spotted
offspring. It is these purses, and those of the thornback and the
edible skate, that we oftenest pick up on the English coast. The larger
oceanic sharks are mostly viviparous.

In some few cases, indeed, among the shark and ray family, the
mechanism for protection goes a step or two further than in these
simple kinds. That well-known frequenter of Australian harbours, the
Port Jackson shark, lays a pear-shaped egg, with a sort of spiral
staircase of leathery ridges winding round it outside, Chinese pagoda
wise, so that even if you bite it (I speak in the person of a
predaceous fish) it eludes your teeth, and goes dodging off
screw-fashion into the water beyond. There's no getting at this evasive
body anywhere; when you think you have it, it wriggles away sideways,
and refuses to give any hold for jaws or palate. In fact, a more
slippery or guileful egg was never yet devised by nature's unconscious
ingenuity. Then, again, the Antarctic chimaera (so called from its very
unprepossessing personal appearance) relies rather upon pure deception
than upon mechanical means for the security of its eggs. The shell or
case in this instance is prolonged at the edge into a kind of broad
wing on either side, so that it exactly resembles one of the large flat
leaves of the Antarctic fucus in whose midst it lurks. It forms the
high-water mark, I fancy, of protective resemblance amongst eggs, for
not only is the margin leaf-like in shape, but it is even gracefully
waved and fringed with floating hairs, as is the fashion with the
expanded fronds of so many among the gigantic far-southern sea-weeds.

A most curious and interesting set of phenomena are those which often
occur when a group of fishes, once marine, take by practi