WORM NODULES IN AUSTRALIAN CATTLE. 345 



Figure 29. Fully developed lar\a from lymph space, 0.12 mm. from peri- 

 phery of nodule, x 610. 



,, 30. Small portion of section of periphery of much thickened wall 

 of a large nodule, showing its structure and larvae lying 

 in lymph spaces close to surface, x 100 (approx.) 



,, 31. Section of large less thickened artery, showing larva' in periphery 

 of wall. X 100 (approx.). 



,, 32. Transverse section of body of worm lying in tunnel. To show 

 general structure and protozoan parasites lying in one- 

 genital tube. X 105. 



,, 33a j 



,, 33b [ Transverse sections of lateral field, showing variations, x 105.. 



„ 33c ) 



,, 34. Section to show- a symmetry and special development of ex- 

 cretory tissue on one side, x 105. 



,, 35. Transverse section through excretory bands carrying excretory- 

 canals towards mid-ventral line to excretory pore, as shown 

 by dotted lines compiled from succeeding sections, x 112. 



., 36. Diagram to show general relations of nervous and excretory 

 tracts in greater portion of body. 



,, 37. Transverse section through male and female worms (anterior 

 ends) and body of male, x 190. 



14.— THE PROBABLE INFLUEN'CE OF RADIO-ACTIVITY IN 



Plates XXII.— XXXVell. 



is an hypothesis of great interest and well worthy of consideration.. 

 In no way would such a problem conflict with Darwinism and its 

 allied theories, but it would be an important additional causal 

 factor in the origin of species and in the development of at least 

 some of their primary characteristics. 



Radio-activity, that is, the production of a, /3 or -/ rays, was 

 first recognised by its artificial production in the laboratory, but 

 this discovery was soon followed by its recognition in nature in 

 certain metallic ores. Nature's radio-activity has been traced to 

 various radio-active substances, polonium, uranium, thorium, 

 radium and actinium ; all of these give out a activity, all except 

 polonium ^ activity, but only radium, and probably actinium, 

 create o^ activity. Minute quantities of these substances are found 

 in most parts of the world, and also in certain natural springs and 

 waters. All of these elements are undergoing constant change, and 

 there is constant definite loss of particles, which must cause their 

 final dissipation. Radium and uranium have been most studied. 

 Frederick Soddy was the first to hold that uranium changes into 

 radium, and Strutt and Bottwood, by an interesting series of 

 deductions, have proved the fife of uranium is 2,500,000 times the 

 life of radium. The most recent calculations as to the life of radium 

 are that it is 1750 years, or that one gramme of radium loses .6 

 milligramme in weight per annum. It is thus evident that the 

 radio-active elements have a definite life before they pass on into the 



