It may, of course, have the power of sinking itself much lower than I have seen it do.

When it is in this state, the apparatus with which it fills the float remains behind the peduncle in a state of perfect quiescence.
The scarlet fluid emitted by this animal is of such a consistency that it can be drawn away from it out of the water, like a glutinous thread.
A part of the animal requires attention, it is composed of an outer cup, or circular lip, which it has the power of contracting or expanding in the same manner as the valve; and when opened out like a cup, an orifice can be seen at the bottom of it.

It can also expand, and make broad the arm; and it then appears to use them as sails.
This species of Janthina, I afterwards found, has the power of in some manner taking in by suction a quantity of water, which it can suddenly expel again with great violence, sending it out as if from a squirt.
We caught, also, an extraordinary fish this day.

Its mouth has the appearance of being situated on its back; a fin, 0.4 inches in length, projected directly out from one side of the fish, and there was every appearance of a perfectly similar one having been torn from the other side; a hard horny membrane projected from underneath the stomach of the animal, being apparently a sort of fin.
Its colour was of a silvery metallic lustre, having in parts a burnished appearance, except where it is shaded (see Illustration 5 and below) and then it was of a dark green colour; the tail was perfectly transparent, except just where it joined the body, and there, where the shaded line is, it was dark green.
This fish was swimming about, apparently preying on the tentaculae of the barnacles, of which there were numbers round the ship attached to the dead Velella, some of which I had caught yesterday; it appears therefore probable that its mouth was placed in so extraordinary a position to enable it to seize this pendant prey.
We caught this day a number of Velella, which are furnished with crests; some of them were dead, and nearly always when such was the case we found a species of barnacle attached in great numbers to them.

When these animals had only recently died, so that the whole of their blue base had not been detached from them, the barnacles were generally very minute, so that the naked eye could only just detect them, and there were no large barnacles on the same fish: now, how did the minute ones get there?
As the barnacles grew larger, the remains of the velella changed into large excrescences, half the size of a walnut.
We caught also several little animals, all of the same species, which swam about on the surface of the water with the greatest rapidity, performing the same kind of evolutions that we see in a little black and white insect (Gyrinus) which swims on the top of tranquil pools in England.
July 16.
This day a curious animal was caught, perfectly diaphanous; total length 0.8 inch; length of third leg, 0.4 inch; this was provided with a claw like a crab; head shaped like a grasshopper, 0.2 inch in length, and placed like the head of a grasshopper, at right angles to the body; eyes black and prominent, apparently four, two on each side; first and second legs of nearly the same length; the third leg nearly double the length of either of the others; five on each side.