The Dawn of Reason | Page 8

the distance of eighteen or twenty
inches. I have often watched them at such times, and have been highly
entertained by their actions. The emotional natures of snails, as far as
love and affection are concerned, seem to be highly developed, and
they show plainly by their actions, when courting, the tenderness they
feel for each other. This has been noticed by many observers of high
authority, notably Darwin, Romanes, and Wolff.[11] Mantagazza, a
distinguished Italian scientist, in his Physiognomy and Expression,
writes as follows: "As long as I live I shall never see anything equal to
the loving tenderness of two snails, who, having in turn launched their
little stone darts (as in prehistoric times), caress and embrace each other
with a grace that might arouse the envy of the most refined
epicurean."[12]
[10] Lubbock, loc. cit. ante, p. 140.
[11] Romanes, Animal Intelligence, p. 27.
[12] Mantagazza, loc. cit., p. 97.
Darwin tells us that two snails, one of them an invalid, the other in
perfect health, lived in the garden of one of his friends. Becoming

dissatisfied with their surroundings, the healthy one went in search of
another home. When it had found it, it returned and assisted its sick
comrade to go thither, evincing toward it, throughout the entire journey,
the utmost tenderness and solicitude.[13] The healthy snail must have
used its sight, as well as its other senses, to some purpose, for, if my
memory serves me correctly, we are told that the sick snail rapidly
regained its health amid its new surroundings.
[13] Darwin, Descent of Man, pp. 262, 263.
The crayfish also has its eyes at the tips of eyestalks, but the eyes of
this creature are very different, indeed, from the eyes of the snail. They
are what are known as compound eyes, a type common to the crayfish
and lobster families. Viewed from above, the cornea of a crayfish is
seen to be divided into a number of compartments or cells, and looks,
in this respect, very much like a section of honeycomb. The microscope
shows that in each one of these cell-like compartments there is a
transparent cone-shaped body; this is called the crystalline cone. The
apex of this cone is prolonged into an exceedingly small tube, that
enters a striped spindle-like body called the striated spindle; the entire
structure is called a visual rod. Nerve-fibrils emanating from the optic
nerve enter the striated spindle at its lower extremity, and in this way
nervously energize the visual rod. There is a deposit of pigment about
the visual rod which arrests all rays of light save those which strike the
cornea parallel to the long axis of the crystalline cone. We see from this
that the visual picture formed by a crayfish's eye must be made up of
many parts; it is, in fact, a mosaic of hundreds of little pictured sections,
which, when united, form the picture as a whole. Each visual rod
receives its impression from the ray or rays of light reflected from the
object viewed which strike it in the line of its long axis; the other rays
are stopped by the layer of pigment-cells. When the impressions of all
the visual rods are added together, the sum will be a mosaic of the
object, but such a perfect one that the junction of its many portions will
be absolutely imperceptible.
The crayfish can see quite well. It has been thought that this creature
uses its sense of smell more than its sense of sight in the procurement

of its food. This is undoubtedly true where the animal is surrounded by
water that is muddy, or that is otherwise rendered opaque. The
odoriferous particles coming from the food being carried to the creature
by the water, it follows them until it arrives at this source.
It is different, however, in clear water and on land. I have seen crayfish
rush down stream after bits of meat thrown to them, thus showing that
here, at least, the sense of sight directed them. Again, I have enticed
crayfish from clear streams by slowly dragging a baited hook in front
of them. Moreover, when high and dry on land, I have seen them
follow with their eyes and bodies the tempting morsel as it waved to
and fro in the air above their heads.
The female crayfish carries her eggs beneath her tail, and, when they
have hatched out, the young find this sheltering member a safe and
cosey dwelling-place until they have grown strong enough to enter
life's struggle. At such times, the mother crayfish is quite brave, and
will do battle with any foe. With her eyestalks protruded to their utmost
extent, she vigilantly watches her enemy. Her eyes follow his
movements, and her sharp nipper is held in readiness