The larger Branchiopoda (Anostraca, Notostraca, and Conchostraca) are generally found in small, shallow ponds which are liable to be dried up in summer. The "Fairy Shrimp" (_Chirocephalus diaphanus_; see Fig. 10, p. 35) has been found in swarms in the water standing in deep cart-ruts in a country lane in England, and _Apus_ sometimes appears suddenly in rain-water puddles of a few square yards in area, which dry up after a few weeks of hot weather. The eggs of these animals, when dried in the mud, may remain dormant for long periods, and many species have been hatched out from samples of dried mud brought by travellers from distant countries. In such a sample from the Pool of Gihon at Jerusalem, it is recorded that the eggs of _Estheria_ (see Fig. 11, p. 36) were found to be capable of hatching after being kept dry for nine years. In some species it is said that the eggs will not develop unless they have been first dried, but this is not the case with _Chirocephalus_. In favourable conditions development takes place very rapidly. Messrs. Spencer and Hall, in describing the Branchiopoda of Central Australia, say: "Certainly not more than two weeks after a fall of rain, and probably only a few days, numberless specimens of _Apus_, measuring in all about 2-1/2 to 3 inches in length, were swimming about; and, as not a single one was to be 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 successive 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 altogether 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.