On this journey, all the beach was, as I have said, covered with water, and I saw no shells; but in the pools on the road were water-beetles swimming about, and these showed a surprising resemblance to the water-beetles of Europe. Gyrinidae swam round and round in mazy circles; Dytiscidae came up to the surface for a moment, and dived down again to the depths below with a globule of air glistening like a diamond. Amongst the vegetation at the bottom and sides of the pools Hydrophilidae crawled about, just as in ponds in England. Not only were those familiars there, but they were represented by species belonging to the typical genera--Gyrinus, Colymbetes, and Hydrophilus. Over these pools flew dragon-flies, whose larval stages are passed in the water, closely resembling others all over the world. All the land fauna was strikingly different from that of other regions; but the water fauna was as strikingly similar. The sameness of fresh-water productions all over the globe is not confined to animal life, but extends to plants also. Alphonse de Candolle has remarked that in large groups of plants which have many terrestrial and only a few aquatic species the latter have a far wider distribution than the former. It is well known to botanists that many fresh-water and marsh plants have an immense range over continents, extending even to the most remote islands.* (* Darwin "Origin of Species" page 417.) The close affinities of fresh-water animals and plants have been noticed by many naturalists. Darwin saw with surprise, in Brazil, the similarity of the fresh-water insects, shells, etc., and the dissimilarity of the surrounding terrestrial beings compared with those of Britain.* (* Darwin "Origin of Species" page 414.) Dr. D. Sharp informs me that water-beetles undoubtedly present the same types all over the world. He believes there is no family of Coleoptera in which tropical or extra-tropical species so closely resemble one another as in the Dytiscidae. Cybister is found in Europe, Asia, Africa, Australia, New Zealand, Brazil, and North America; and the species have a very wide range. Dr. Sharp remarks that this wide distribution and great similarity of the Dytiscidae is of special interest when we recollect that they are nothing but Carabidae fitted for swimming, and yet that the Carabidae are one of the groups in which the tropical members differ widely from the temperate ones.