Some species of _Branchipus_ (e.g. _B. spinosus_, M. Edw.) and of _Estheria_ (_E. macgillivrayi_, Baird, _E. gubernator_, Klutzinger) occur in salt pools, but _Artemia_ flourishes in waters beside whose salinity that endured by any other Branchiopod is insignificant. In the South of Europe, _Artemia salina_ may be found in swarms, as it used to be found in Dorsetshire, in the shallow brine-pans from which salt is commercially prepared; Rathke quotes an analysis showing that a pool in the Crimea contained living _Artemia_ when the salts in solution were 271 grms. per litre, and the water was said to have the colour and consistency of beer. The behaviour of the animals in the water differs a little; in normal feeding all the species swim with the back downwards, as has already been said; the Branchipodidae rarely settle on the ground, or on foreign objects, but the Apodidae occasionally wriggle along the bottom on their ventral surface, and _Estheria_ burrows in mud. The greater number of species are found in pools in flat, low-lying regions, and many appear to be especially abundant near the sea; _Apus cancriformis_ has, however, been found in Armenia at 10,000 feet above sea level. Wells and underground waters do not generally contain Phyllopods; but a species of _Branchipus_ and one of _Limnetis_, both blind, have been described from the caves of Carniola. One of the many puzzles presented by these creatures is the erratic way in which they are scattered through the regions they inhabit; a single small pond, a few yards or less in diameter, may be the only place within many miles in which a given species can be found; in this pond it may, however, appear regularly season after season for some time, and then suddenly vanish.