386 Hilda Kincaid : 



In this talkie, as in the precedinijj one, several interesting 

 points should be noted : — 



1. A marked difference between the magnitude of the P.^O,, 

 content of the skeleton of the Vertebrates and Invertebrates. 

 Thus even in the shark where cartilage takes the place of true 

 bone there is a sudden and unmistakable rise from the per- 

 centage in even the highest gToup of the Invertebrates ; the 

 metapterygium of the shark (a fairly young female) giving 32 

 per cent. P^O., in the ash, and about 8.9 per cent, in the dried. 



2. Tracing up the ascending groups of the Vertebrata, we 

 find a marked rise from the cartilaginous to the bony fishes ; 

 but from there right on through amphibia, aves and mammalia, 

 there is no very great variation, at any rate in the percentage 

 value in the ash. 



The cartilaginous fishes seem to stand in this i-espect midway 

 between the main body of the Invertebrates on the one hand, 

 and of the Vertebrates on the other — the Invertebrates, which 

 have not yet learned the knack to any extent of utilising phos- 

 phorus in the skeleton, and the Vertebrates which have appa- 

 rently early learned (even as early as the fishes) to utilise this 

 element, and learned moreover to use it in amount best suited 

 to the requirements, since from the fishes right on through the 

 higher groups there is scarcely any variation ; any small varia- 

 tions which do occur might easily be due to differences in food 

 and environment. Although calcium phosphate is much 

 superior to calcium carbonate, in that it can be kept much 

 more readily in colloidal form than the cai-bonate can, and the 

 characteristic rigidity and elasticity of bone can be maintained ; 

 yet this colloidal calcium phosphate is very unstable and con 

 stantly tends t(t slip into the crystalline form. Thetheory may beput 

 forward that in the bones of animals this crystalline form is at once 

 removed by the blood, and excreted as quickly as it is formed, 

 and fresh colloidal phosphate takes its place, and thus is ex- 

 plained the necessity for metabolism in bone. In old age tlie 

 replacement of the crystalline by colloidal is less efficient, and 

 hence the bones become brittle. 



G. — Phosphorus in Au.stralia prom an Economic View Point. 



At the beginning of this paper it Avas pointed out that Aus- 

 tralian soils as a whole are very hjw in phosphorus content, but 



