26 BRITISH ENTOMOSTRACA. 



upon the edges of the ponds, and nearly on the surface 

 of the water, but in stormy or cold weather they are no 

 longer to be seen." They can swim as freely upon their 

 back as on their inferior surface, and in both these posi- 

 tions we may see their feet continually in motion, alter- 

 nately from below upwards, and from right to left, 

 fatiguing the eye to follow them. Indeed their branchial 

 feet seem never at rest, for when the animal no longer 

 uses its rami, but floats idly on the water, these organs 

 are still in rapid motion, causing a sort of whirlpool in 

 the water, and attracting towards their mouth the objects 

 floating about them. Their chief food appears to be the 

 smaller species of Entomostraca, which generally are 

 found in great abundance in the same places, such as 

 Daphnise and Cyprides, the shells of which latter little 

 creatures they can easily break down by means of their 

 strong mandibles. Schceffer says they perish very quickly 

 after being taken out of the water, or when the ponds 

 dry up. It appears, notwithstanding, that after a pond 

 has been dried up for some time, and suddenly filled anew 

 by heavy rain, in two days these animals will be seen in 

 abundance. The eggs certainly retain their vitality long 

 after being dried, for these little creatures have been 

 known to appear in a ditch that was suddenly filled with 

 water after having been dried up for two or three years. 

 Frogs seem to be their chief enemy, and they are gene- 

 rally to be met with in a more or less mutilated state. 



Professor Retzius, at the meeting of the German natu- 

 ralists at Breslau, in September, 1833, announced that 

 M. Kollar, of Vienna, had discovered the male of the 

 Apus cancriformis, but I have not been able to find any 

 detailed description of it.* 



SchoofFer, Berthold, and Zaddach had considered them 

 to be hermaphrodites ; but in all probability the males 

 will be found, as in the case of the Daplnme, to exist at 

 some particular season of the year, and perhaps in small 



*Isis, 1S31, p. 680; I'Wirp's Notizeu, 1833, pp. 38, 118; Durmcister, 

 Organ, of 'Mobiles, Kay Soc. rdit., p. 10, IS 10. 



