1922. | Mound-building Birds of Australia. 709 hatching them by means of heat produced by the fermentation of organic matter, or whether it was a parallel development. This we can be certain of, viz., that the collecting together of dead leaves into heaps in order that fermentation may be induced, then the awaiting of the time when the necessary heat was generated and the ascertaining of the correct time when the ferment was on the wane and it became safe for the deposition of the eges, shows an intelligence of a very high order. / The case of the Leipoa is still more remarkable. That the ‘ainfall has greatly decreased in the interior of Australia has been sufficiently demonstrated. By reasonable deduction we are safe in asserting that the vegetation of this area will in the past have more or less corresponded with that which now obtains in the habitats of the Jungle-Fowl and the Brush-Turkey.

We are certainly justified in concluding that the Mallee-Fowl, in common with the above-named genera, originally depended entirely for the incubation of its eges on heat generated by fermenting organic matter. With the reduction of the rainfall a great change took place in the vegetation, ultimately fewer and fewer eggs laid by the Mallee-Fowl were successfully hatched, and the birds were confronted with extermination. There could’ have been only two alternatives, either a reversion to the methods common to other birds, viz., that of incubation by means of body-heat or the discovery of some new means whereby the temperature of the mounds could be raised. This difficulty has been met and overcome by these intelligent birds in the utilization of solar heat. It will be remembered that conjointly with the reduetion of the rainfall came an increase in the periods of clear sky and bright sunshine.

I submit that there is sufficient ascertained data to warrant us in piecing together this page in the past history of the Leipoa. It certainly forms one of the most intelligent and remarkable cases of the adaptation of habits to changed circumstances that can be found in the whole realm of Nature below that of man.