352 PROCEEDINGS OF SECTION D. 



The development of further appendages — e.g., hair or feathers 

 possessing inhibitory powers and of new habits, e.g., flight, enabling 

 the primitive serpent-like bird to exist mainly outside the sphere 

 of action of a and soft and medium (■i activity or swift motion, 

 enabling the possessor to cross rapidly acutely radio-active areas — 

 all modified the reaction to radio-activity in different ways by 

 exposing the organisms to different intensities of activity. In 

 new spheres of activity, not only were different reactions effected, 

 but the results of former reactions were discarded as useless, c.f., 

 the thickened epidermis of the primitive bird. 



It must now be remembered that a, soft medium and hard (i, 

 and 7 activity individually possess gradually increasing co-efficients 

 of absorption. Further, taking the rays emitted from radium in 

 the laboratory as an example, « rays constitute 90 per cent, of the 

 radiations, (3 9 per cent., and 7 1 per cent. ; it is evident thatn rays 

 are the commonest, and 7 rays the rarest. This proportion in nature 

 is still more accentuated by polonium giving a rays only and 

 radium and actinum alone causing 7 rays. From these facts it is 

 clear that as the fauna increased in size and developed thickened 

 superficies, their central parts received less and less radio-activity, 

 and in consequence were enabled to develop more highly specialised 

 cells of less molecular stability, being further removed from the 

 destructive influence of irradiation, and the natural evolution of 

 organs of special function was only slightly malverted. 



Following the natural laws of evolution the minor special 

 organs reached perfection before the more highly speciahsed, and 

 the last to become evolved to any considerable degree were the 

 special centres of the nervous system. After noting the results of 

 Danysz, London, and others on the experimental reaction of the 

 nervous system to irradiation, it is reasonable to assume that the 

 development of the brain was inhibited whilst radio-activity was 

 excessive, and high mentality was incapable of development, and 

 the mental characteristics of the period were slow cerebration, 

 similar to that produced in the laboratory by London, with the 

 mental functions restricted to the vital processes of life and the 

 simpler instincts. Those types which developed the more thickened 

 and completely enclosed bony carapace had the greater chance of 

 mental development. 



During this and the preceding period it is probable that life 

 was exposed to few accidents to health, since it has been shown in 

 the laboratory that the virulence of the micro-organisms of disease 

 is attenuated and the toxicity of animal poisons, e.g., snake venom 

 is destroyed by radio-activity, and this was probably reproduced in 

 nature. As a result the normal period of hfe was extended with, 

 as a natural sequence, greater time for development. 



During this period vast changes occurred on the earth's surface, 

 and areas of comparative safety from radio-activity were created, 

 the most important being the deposit of the coal beds, which 

 strongly filtered radio-activity itself and absorbed the emanations. 



