BY HEBER A. LONGMAN. 35 



Darwin. Endeavours were made to read into all extinct 

 forms some lineal association with modern organisms. This 

 resulted from a very natural idea that our modern world 

 with its fauna and flora was in reality the siunmum honum 

 of all life and that the processes of nature, without excej)tion, 

 were so arranged as to establish a suitable environment for 

 man. Xow we have somewhat to amend this view. We 

 cannot always judge the past by the present. In each era 

 life has radiated out apparently to the full gamut of 

 potentiality. There have been rich developments of cer- 

 tain groups in different periods. One may note such well- 

 known instances as the abundance of Trilobites in the 

 <"ambrian, Dipnoid fish in the Devonian. Xavtiloidea in the 

 8ilurian and Ammonoidea in the Trias. .Systematists have 

 already noted about oOOO species of Ammonites, and so 

 abundant is material that the evolution of the group from 

 its origin to its extinction has been well worked out. Some 

 of the forms were very highly specialised, and the maze of 

 their sutures — often beautifully shown in our Queensland 

 Cretaceous specimens — demonstrates an organism of great 

 complexity. The protean development of marine, land 

 and air forms of reptilian life in Mesozoic times exhausts 

 the most superlative of adjectives when description is 

 attempted. The great majority of these forms were lateral 

 offshoots from the main stream of life, and they have no 

 lineal relationship with the animals of to-day. Many were 

 apparently the victims of over-specialisation, of hy])er- 

 tro])hy. Here the multitude of diverse forms gives evidence 

 of radial evolution, of wild exuberance of life flourishing 

 for a time until cut short by the iron laws of natural selec- 

 tion. And in the succeeding age of mammals we find a 

 similar story. Tertiary times show a rich development 

 of mammalian life, including gigantic types, and many of 

 these were not potential for the future. Certain forms 

 came upon the stage of existence, played but a brief part, 

 geologically speaking, and then disappeared. These were 

 the derelicts of nature, the failures in the struggle of life. 

 Yet they were no weaklings, and some carried a bulk of 

 bone which is astounding. They were not lacking in 

 virility, but in plasticity. Other forms were forerunners of 

 the fauna of to-day ; their very life-blood runs in present- 



