The sea was, this morning, covered in places with fleets of the Velella of Lamarck; also with great numbers of the species of Janthina which I described yesterday; to both of these kinds of animals large clusters of barnacles were frequently attached.  These barnacles preyed on the different gelatinous animals which were swimming about.  It was curious to see them seize on these with their hooked tentaculae and draw them in, whilst the acalepha, or gelatinous animal, contracted and dilated itself with all its might and main, endeavouring to escape.  We saw two or three times very large shoals of porpoises ahead of us, and when we reached the spot where they had been we found the sea quite cleared of the animals with which it was covered in other places, so that we imagined the porpoises must have been feeding on them.  We saw also a whale and a shark today.

Although these little floating animals were so numerous there were but very few of the gelatinous species to be seen, and they were chiefly of the larger sorts.  I saw one of the species (Glaucus) of which I have given a sketch, on the 17th of June.  Like all the animals of this species which we caught to the westward of the Cape it had a red intestinal spot in it; but excepting in its great size it differed in no respect from the others which I had seen:  this one was at least a foot in length.

A number of black minute animals were caught, which, at a rapid glance, looked not unlike fleas with long feelers or antennae.

We caught also this day an animal (Salpa) which consisted of a gelatinous transparent bag, having an orifice provided with a valve that opened and closed the orifice at pleasure; there was no other opening to the sac that I could discover; I passed the end of a pencil down it, but although it passed readily through the valve it could not at first pass through the bottom of the gelatinous sac; but I afterwards found that this was an error, and that the pencil could be passed right through the body of the animal, which was provided with a valve at each end.  I found also that the united animals had the power of swimming with either end foremost.  There was an intestinal tube in the animal of a dark reddish brown colour.  This animal appeared to exist very badly alone, fourteen of them were always found united together by a plane; they then formed a mass shaped like half an orange and having a cup at its upper surface; the intestinal canals, when they are in this position, are all brought near to one another, and the whole mass looks not unlike a flower; they are united to one another by so thick a fluid that it is very difficult to separate them.  If one or more are torn away from the mass the outside ones immediately join together and form a united mass again, of the original shape.  They open the orifices at different times:  that is, two or three open theirs at the moment that some of the others are closing, so that no regular or simultaneous movement takes place between the different animals.  This irregular movement of the animals gives to the whole body an irregular rotatory motion; but when one is separated from the others it can only drive itself round and round upon its own centre, and has not the faculty of propelling itself as the other acalepha have.  They also swim with either end foremost, in the manner the other acalepha do.