British Freshwater Entomostraca. 353 
found the large race (exceeding 20 mm.) the commoner in 
Tunisia; but on one occasion the specimens taken in a 
small rain-pool near Tunis included both large and small 
individuals, and were separable into three groups. Out of 
15 males measured, 12 ranged from 24 to 22 mm., two were 
intermediate (19 and 16 mm.), and one very small (12 mm.). 
The species is found both in muddy temporary pools—such 
as cart-tracks at Claygate—and also in clear, weedy water 
as on Bratley Heath. Brauer gives it as an example of a 
Branchipod of clear water, associated commonly with Lepi- 
durus apus, as compared with Branchipus pisciformis, Schaeff., 
which is found in muddy places in company with Apus 
cancriformis ; but this distinction does not hold good in my 
experience, since in Tunisia it was generally found in muddy 
pools, and more than once in company with Apus cancri- 
jormis. Brauer has also pointed out that the association 
with Apus and Estheria is of direct benefit to the Branchipods, 
since Apus and Estheria stir up the mud and so distribute 
food. It seems to me that there is no dimorphism in the 
case of C. diaphanus, but that the size of the individuals 
depends on the conditions of existence, the larger form being 
generally found in muddy places rich in food and the smaller 
in clear water. 
In France, where C. diaphanus is common, it appears first 
in March, and commonly disappears in summer owing to the 
drying up of the pools. In this country it has been recorded 
in almost every month in the year, but Mr. H. J. Wad- 
dington’s observations * show that, near Christchurch, it 
appears between January and March, disappears in summer, 
and reappears again foratime in autumn. The notes which 
Mr. Lucas has kindly sent me of its occurrences at Claygate 
seem to prove the same kind of cycle, but I do not think 
that the history of any colony has ever been completely 
followed throughout the year. The eggs of C. diaphanus, 
unlike those of most other Phyllopods, do not require to be 
dried before developing, though they can, of course, resist 
desiccation. Brauer states that, when they remain in water 
after being laid, they have a resting period of some mouths; 
and the individuals appearing in autumn would, therefore, be 
derived from the eggs laid in spring. On the other hand, 
Shaw, who gave an interesting account of his observationsf, 
states that eggs laid by a female isolated in an aquarium 
hatch in about a fortnight; and it seems that further 
* Journ. R. Mic. Soc. 1913, pp. 250-254. 
+ Trans. Linn. Soe. i, 1791, pp. 103-110. 
~ Ann. & Mag. N. Hist. Ser. 9. Vol. v. 24. 
