HORN EXPEDITION-AMPHIBIA. 
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a very lieavy rainfall, the creeks and clay-pans were swarming with frogs; but 
though they were so numerous I could only find examples of four species, and no 
trace of any which we had not seen during the dry season ; so that on the whole I 
am inclined to think that, though the number of individuals is considerable, the 
number of species is very few. 
It must be remembered that the central portion of Australia, drained by 
the Finke River and its tributaries, and which adopting the native name of 
the Finke may appropriately be called the Larapintine Region, is now and 
has been probably for long shut off by desert regions from especially the north 
and eastern parts of the continent, where frogs are more plentiful; while 
to the south and west are also vast stretches of desert land continuous in the 
latter direction with the equally dry wastes of West Australia. 
All travellers have been impressed with the remarkable way in which in these 
dry regions frogs appear as if by magic, fully grown, immediately after a heavy 
rainfall, even if this has been preceded by, it may be, two or more years of 
drought. The moment the creeks run and the clay-pans fill, the incessant 
croaking of frogs is heard everywhere. As the water drys up the frogs disappear, 
and remain hidden until the next rainfall. 
Under conditions such as these one of two methods must have been adopted if 
the frogs are to continue living and reproducing in such desert regions. 
They must either have adapted themselves to their surroundings so as to do 
without the tadpole stage passed in the water, that is, they must develope directly 
into the adult without the necessity of the eggs being deposited in water, or they 
must have adopted some habit which will enable them to tide over it may be a 
year or two of drought, and so to wait patiently until there is water enough for 
them to deposit their eggs, and for the latter to develope into tadpoles in the 
ordinary way. 
As Mr. Fletcher says :* “ The rainfall is a most important factor in regulating 
the date of oviposition, inasmuch as a heavy downpour of rain is often necessary 
to release frogs from their aestivation, and in many cases to provide a water supply 
in which the spawn can be deposited. A heavy downpour of rain succeeding a 
period of dry weather will set some frogs spawning at any time of the year; and, 
on the other hand, in whatever month the frogs spawn, as a general rule they do 
so as soon as the weather clears up after rain.” 
* Proc. Linn. Soc. N.S.W., vol. iv., 18S9, p. 362. 
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