We saw also some animals of this class, and nearly as large as the ones I have just described, but they differed in their form and mode of attachment, and joined themselves in long strings, two deep, so as to look like gelatinous snakes.  I have before described animals of this class with blue spots.  I think that a good mode of classifying these animals would be from their form of arrangement when united.

July 17.  South latitude 19 degrees 47 minutes; west longitude 3 degrees 5 minutes 30 seconds.

Found a small animal (Cymothoa) like a wood-louse, similar to the one we caught on the 15th of this month and to another taken on the 21st of November 1837.  It had seven legs on each side, besides the five which when taken out of the water it folded over its abdomen; the colour the same as before described.

Length 0.52 inch. 
Width over broadest part 0.2 inch. 
Length of antennae 0.2 inch.

Illustration 4, exactly the size of life, gives a good idea of it.  It lived out of the water for two or three hours and did not die until put into spirits; it ran about on the table as well as it swam in the water, so that it was evidently amphibious.  It swam about from a dead shell of the Velella, to a nautilus, and from that again to some barnacles; each shell that it reached it climbed up, and folding up its fins ran all over it, so that it appeared like a little navigator which was roving from island to island in the ocean, seeking food and nourishment from all of them.  Are not the ways of nature very wonderful?  This little animal was at least 500 miles from any land, as we term it, yet it was surrounded by sunny islands, teeming for it with the most delicious food, and where it either basked in the warm daylight, or shaded itself in some oozy recess, as seemed most pleasant to it.

When walking on these substances it used its antennae exactly as insects do, and showed an extraordinary degree of susceptibility when touched.  I do not know that I have ever seen an animal which more decidedly evinced an acute sense of feeling and dread of pain.

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 latitude.  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 latitudes.

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 latitudes is very cold at all seasons of the year.

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