162 THE LIFE OF CRUSTACEA 



found in the water-pools prior to the rain, these 

 must have been developed from the egg." 



From what has been said, it is apparent that the 

 larger Branchiopoda are particularly well fitted to 

 be distributed by the agency of birds, and this is no 

 doubt the explanation of the way in which many of 

 the species suddenly appear in localities where they 

 were previously unknown, and, after swarming for 

 a longer or shorter time, sometimes for several suc- 

 cessive seasons, as suddenly vanish. A striking 

 example of this is afforded by Apus cancriformis 

 (see Plate II.), which formerly occurred in several 

 localities in the South of England, and appears more 

 or less irregularly in many parts of the Continent of 

 Europe. No British specimens had been recorded 

 for over forty years, and the species was believed to 

 be extinct in this country, when it was found in 1907 

 by Mr. F. Balfour Browne in a brackish marsh near 

 Southwick, in Kirkcudbrightshire. It can hardly be 

 supposed that so large an animal as Apus, and one 

 so easily recognized, would have escaped notice alto- 

 gether had it occurred regularly in any part of the 

 British Islands. It is much more probable that the 

 Scottish specimens found in 1907 had developed 

 from eggs accidentally transported by some bird 

 from the Continent. In 1908 a careful search 

 in the same locality failed to reveal a solitary 

 specimen. 



The Anostraca and Notostraca usually swim with 



