II HABITAT OF PHYLLOPODA ars 
the course of their lives. My friend Mr. W. 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 this happened in a small aquarium in 
my laboratory, in which Chirocephalus diaphanus 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°5 grm. salts per litre, the chlorine being equiva- 
lent to 0:023 erm. 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, the Chirocephalus being still active ; 
the residue contained 0°96 erm. 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 Branchipus (e.g. B. spinosus, M. Edw.) and 
of Estheria (FE. macgillivrayi, Baird, FL. gubernator, 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 ; 
Rathke quotes an analysis showing that a pool in the Crimea 
contained living Artemia when the salts in solution were 271 
erms. 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 alone the bottom on their ventral surface, and Hstheria 
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 
