20 .]1(H!N K.XPKDITION — NAliliATIVK. 



case two days would !io enou^li to hatch out (lie eggs. If the hot day lasted six- 

 teen liours, and heated a pond to 27", while the night in which the watec cooled to 

 IS ■ lasted eight hours, then an easy ealcidation would show that the time should 

 he about fifty-tive hours. Probably it is an essential to the reproduction of these 

 creatures that they sliould spawn in liot weather and so secure the adxantage of a 

 two days period of incubation." 



I liave not yet had the oiiportuiiity of testing the rapidity with which the 

 fi'ogs' eggs develop in the clay-pans and water luiles of Central Austi-alia, but as 

 the rains fall during the liottest pai't of the year, when even at night-time the 

 temperature remains Jiigh, there can be little doubt that tlie temiieratuie of the 

 water is exceedingly favourable to a rapid dcAclopment, and (lier(> is no doubt 

 whatever tliat this i";ipid development does take |ilace ; in fact, if the animal is to 

 liave any chance of sur\i\ing it must do so. 



Amongst the Aitliropoda the most striking form is Apus (A. ni/sfrn/ieiisis), 

 which is often seen coming to the surface, where it swims about on its back, its 

 red appendages rendering it easily seen from above, whilst from beneath its 

 yellow carapace may perhaps serve at once to liide and to protect it from its 

 enemies, tlie voracious water-beetles, which are darting up and down. Vaiious 

 species of bivalved Crustaceans, some three-quarters of an inch in length, swim 

 about. One form, JEs/Iicria /^ackardi, is pi'esent in great num))ers and persists long 

 after the other forms have disappeared from the water and are represented only 

 by their empty carapaces. This and some of the others ha\e red blood, but the 

 larger forms, whicli are much rarer (belonging to a new genus, Limnadopsis), liave 

 quite colourless blood. 



All these Crustacea for some reason seem to pr(^fcr muddy water. Fi'om the 

 Macumba River, during the summer time, when it was in flood and the water was 

 muddy, I secured specimens of all of them, but searching in the same water-holes 

 two or three weeks later, when the water was clear, there was not one to be 

 found though they were still alive in the muddy clay-pans close by. 



The contrast between the way in wliicli Apus and the Estherias swim is very 

 marked, the former on its back with the feet uppermost and the latt(>r witii the 

 feet lowermost. The diiference is probal>ly assf)ciated with the fact that the two 

 halves of the Estheria carapace can be compk^tely closed over tlie animal's body 

 for protection, whilst such closure cannot take place in the case of Apus, whose 

 .soft and blood-red appendages are very prominent and would be constantly seized 

 upon by the voracious water-beetles if it swam on the surface with its back 



