Here the series is perhaps most deficient. This is to be expected, being that the invertebrates compose the vast majority of life forms, and it is not probable that they all would have received the same emphasis as have the vertebrates. Evidence is presented to show South American and African affinities between various invertebrate fauna. Yet one could wish that the treatment here was more extensive. Section four concerns itself with the biogeography of fresh waters.
Australian rainfall is largely seasonal and in most areas erratic in amount.
This has resulted in a large number of organisms which have highly specific capabilities in coping with this seasonality. It is unfortunate that the biogeography of marine organisms was not treated, for there are numerous forms that have poor dispersal properties which inhabit the coastal shores, especially the Great Barrier Reef, and these certainly could have been examined with profit. Sections five and six deal with the poikilothermic and homeothermic vertebrates respectively. The amphibians are logically dispersed in accordance with the abundance of moisture. Both the amphibians and reptiles show supposed mixed origins, a few with affinities to proposed Gondwanaland fauna and a majority having Asian affinities.