II HABITAT OF PHVLLOPODA 33 



the course of their lives. My friend Mr. AV. W. Fisher points 

 out that the plants present in such a pond would often precipitate 

 the carbonate of lime, so that this might be removed as evapora- 

 tion went on, but that chlorides would probably remain in solu- 

 tion ; from analyses which Mr. Fisher has been kind enough to 

 make for me, it is seen that tliis happened in a small aquarium in 

 my laboratory, in which Chirocej^halus diapliciniis lived for four 

 months. In April, mud from the dry bed of a pond, known to 

 contain eggs of Chirocephalus, was placed in this aquarium in 

 Oxford, and water was added from the tap. Oxford tap-water 

 contains about 0"3 grni. salts per litre, the chlorine being equiva- 

 lent to 0'023 grm. NaCl. Water was added from time to time 

 during May and June, but in July evaporation was allowed to 

 proceed unchecked. At the end of July there was about half the 

 original volume of water, tlie Chiroccj)halus being still active ; 

 the residue contained 0'96 grm. dissolved solids per litre, with 

 chlorine equal to 0"19 grm. NaCl, so that the percentage of 

 chlorides was about eight times the initial percentage, but there 

 were only three and a fifth times the original amount of 

 total solid matter in solution, the carbonate of lime having pre- 

 cipitated as a visible film. 



Some species of Branchijnis (e.g. B. spinosus, M. Edw.) and 

 of Estheria (U. macgillivrayi, Baird, E. gtiberiiator, Klutzinger) 

 occur in salt pools, but Artemia flourishes in waters beside 

 whose salinity that endured by any other Branchiopod is in- 

 significant. 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 ; 

 Eathke cpiotes 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 



VOL. IV D 



