British Freshwater Entomoslracn. 353 



found the large race (exceeding 20 miu.) the commoner in 

 Tunisia; but ou one occasion the s[)ecimcns 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 comparedwith Branchipus pisciformis, Schaeff., 

 whicli is found in muddy places in company with Apus 

 cancriformis ; but this distinction does not hold good in my 

 experience, since in Tunisia it Avas generally found in muddy 

 pools, and more than once in company with Apus cancri- 

 formis. 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. diaphajius, 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 ^larch, and commonly disappears in summer owing to the 

 drying up of the pools. In this country it has been recorded 

 ill 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 for a time in autumn. The notes whicti 

 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 tlie 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 slates that, when they remain in water 

 after being laid, they have a resting period of some months; 

 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. 11. Mic. Soc. 1913, pp. i'50-2r)4. 

 t Trans. Linn. Soc, i. 1791, pp. 103-110. 



Ann. (0 Mlkj. N. IJist. Ser. 0. Vul. v. 24 



