200 



views that all space-lattices should really be pseudo-cubic *), or that 

 all higher symmetrical crystals should only be pseudo-symmetrical 

 aggregations of submicroscopical lamellae of lower symmetry, is 

 a long way. A rational proof of these views cannot at present be given, 

 and as such these hypotheses have no immediate value for our know- 

 ledge in its present state. But even if we leave these views aside, it 

 can only be once more emphasised, that the idea of lamellar aggre- 

 gation has been, and in future will prove, a very successful one in 

 the explanation of a great number of the most interesting phenomena 

 in the science of inorganic matter. 



13. In this and the preceding chapters we were able to compare 

 on several occasions the specific symmetry of objects in inanimate 

 and in living nature. As strikingly different features of the sym- 

 metry-properties revealed in both domains we must chiefly bear in 

 mind two important facts: 1) the occurrence in living nature of 

 symmetry-axes which are characterised by irrational values of the 

 cosines of their periods n\ and 2) the much higher symmetry of the 

 older species of animals, in comparison with that of the living beings 

 of later periods of evolution. Indeed, after what we have seen in 

 the last chapter, in non-living nature there seems to be rather an 

 oppositely directed tendency, a drift towards the highest degree of 

 symmetry possible 2 ). The cases of apparent and mimetic symmetry 

 dealt with in the above may serve to sustain this view; further the 

 fact that polymorphic substances generally change into higher 

 symmetrical forms, when temperature increases. In the next chapter 

 we shall obtain yet more evidence for this view: we shall see, that 

 optical antipodes, possessing only symmetry-properties of the first 

 order, have also a natural tendency to pass into optical ^active 

 systems exhibiting symmetry-properties of the second order. A cer- 

 tain tendency to form the more symmetrically built molecules in cases, 



!) E. Mallard, Bull, de la Soc. Miner., 7, 349, (1884); 9, 54, 123, (1886); 

 F. Wallerant, ibidem, 24, 159, (1901). 



This theory, however, has in recent times gained a new support, although in some- 

 what modified form, by the dynamical views of J. Stark. According to this investi- 

 gator, rocksalt for instance, would be built up by three submicroscopical systems 

 of tetragonal-hemimorphic symmetry. They form a quasi-homogeneous complex 

 of apparently holohedral cubic symmetry. Similar ideas are found in a paper of 

 J. Beckenkamp (Cf. : J. Stark, Jahrbuch fur Radioaktiv. und Elektronik, 

 12, 280, (1915). 



2 ) Cf. also: G, Bohn, "La naissance de I' intelligence" , Paris, (1917), p. 113 138. 



