Volume II Part 13 (1/2)

The animal here described belongs equally to the Indian and Atlantic Oceans, and appears, as far as my experience goes, never to venture to the south of 25 degrees south lat.i.tude. This is now the third species of animals which I have found to be common to the Atlantic and Indian Oceans, and which never venture beyond the warmer lat.i.tudes.

The question is how they got round the Cape of Good Hope, or Cape Horn?

Might we not hence infer that there was a time when the continent of Africa did not exist? and might not this argument be much extended? It could be combated by none of those causes which are advanced relative to the distribution of species on land; for,

1. The temperature of the water in southern lat.i.tudes is very cold at all seasons of the year.

2. These animals are extremely susceptible of all changes of temperature.

3. They have no means of warming themselves by exercise or motion.

4. The species of food which they subsist on is confined to the lat.i.tudes in which they themselves live.

5. They would have to traverse great distances in ungenial climes, and contend against adverse winds, the children of placid seas and genial suns hurried into giant waves and chilling storms.

6. It is not probable that they are swept along in currents, from the circ.u.mstance that in the one which flows along the coast to the eastward of the Cape we could find none of them, whilst upon its very edge they were in abundance.

Could however their eggs be swept along by a current, and after having been wave-tossed for months or years, be at last borne into waters sufficiently warm to hatch them, and the animals, finding themselves in a genial climate, have increased and multiplied?

The numerous little animals of the species which I have always considered to be the Velella of Lamarck went sailing merrily by us today; the least breath of wind made them turn round and round; and this was their mode of progression, the animal moved its little sail which I have before mentioned, and worked its tentaculae so vigorously as to make ripples in the water, in the midst of which it went buoyantly floating along.

Caught another fish (Stenopteryx Ill.u.s.tration 5) of the same species as that found on the 15th of July. The accompanying figure is drawn from minute measurements. The length of this specimen was 2.5 inches, its thickness through the thickest part 0.38.

What I had before imagined to be either a spine or fin turned out to be a pectoral fin.

It thus has two pectoral, one dorsal, and one ventral fin, properly speaking; but the greater part of the body is surrounded by some cartilaginous substance which it probably uses as a fin; under the line b c there is a curved portion of this matter, and above and attached to the fish is a line of round white silvery scales, about ten in number.

Between a and b there is another curved ma.s.s of transparent cartilaginous substance, along the bottom of which runs a spine to which is attached a fringe-like fin. There is a spine upon the back; the eye is very prominent and bright; upon the back, between the eye and the spine, there are successive stripes of purple and burnished gold, so that this little animal is one of the most gorgeously coloured denizens of the ocean. It swims about amongst the purple barnacles and pink nautili, seeking on the sh.o.r.es of these s.h.i.+ning islands its prey, the curious formation of its mouth being admirably adapted to enable it, whilst swimming under these painted floating islands, to crop off what it lists.

There were scarcely any gelatinous animals in the sea this day; but many Janthina sh.e.l.ls and Velella were round the s.h.i.+p, to which were attached barnacles of different species; amongst this group of islands numerous crabs were swimming about and running over them. Animals resembling a wood-louse were also in the sea, swimming and running about the floating sh.e.l.ls and barnacles.

We caught also a new species of Janthina, the float of which, instead of being nearly round and extending over the sh.e.l.l on each side, was spread like a spiral fold from the sh.e.l.l; the breadth of this fold was 0.45 inch, close to the mouth of the sh.e.l.l, and it gradually tapered off to a point, its length being 3.6 inches. This float being curved round like the tail of an animal, the whole thing bore the appearance of being a sort of snake, of which the sh.e.l.l was the head; the sailors called them caterpillars before I had examined them. The float was composed of two parts, one of which was only froth and the other was apparently some extraneous substance attached to the froth. The sh.e.l.l is very different from those of the other nautili in being much more deeply indented with circular striae.

July 18. South lat.i.tude 19 degrees 49 minutes; west longitude 3 degrees 10 minutes 15 seconds.

We have lately caught several specimens of Creseis. Each consists of a cylindrical tube, increasing in size from its broadest extremity to the centre where it is thickest, and decreasing from the centre to its other extremity, where it becomes a fine point. It is throughout its extent gelatinous, transparent, and of strong consistency.

There is apparently a valve at its broadest extremity.

Length 1.1 inch.

Breadth in centre 0.1 inch.

Breadth at mouth of wide extremity 0.08 inch.

We have several times caught a triangular, transparent, gelatinous animal; it is 0.18 inch in thickness, and in the outer pulpy gelatinous ma.s.s there is an interior sac, and strong muscular bands are marked across this. The sac is composed of three lobes, two of which have apparently no external opening, whilst at the end of the main lobe there is one which closes with a valve; through this I have seen them take in little animals, which reached no farther than the centre, from which the lobes radiate, when the sac became violently agitated, and made strong efforts to expel the foreign substance. This animal was very sensitive, more particularly about the opening of the entrance.

We caught today the lower part of the species of Diphyes which we had found on the 13th November 1837, in 30 degrees 7 minutes south lat.i.tude, in the Indian Ocean. This animal is thus distributed over a wide range.

We also found a very minute species of the animal similar to one which we caught on July 1st 1840. Those we caught today were scarcely 0.05 inches in diameter. They unfolded little wings and flew with them in precisely the way those did which I described on that day.

Nothing I have seen is more remarkable than the flight of these little animals; their wings are milk white and very large for their body, and as they fly, the ends, from their pliancy, bend over, which imparts to the motion a very graceful appearance; these wings are composed of a very fine membrane like that forming the wings of a bat. At one time these little animals hovered over a single spot like a bird of prey in the air, flapping their wings in just the same manner. At another time they darted forward with great rapidity, and the vibration of their wings was so rapid that I could not count them. When folded up they look like very minute gelatinous animals with a black internal spot, but when touched their sh.e.l.l can be felt. We saw a shoal of whales today.

We have caught lately a great many small animals, of which the following is the description; they swim about from one floating substance to another and are eaten by the little crabs which are numerous in these seas.