January 25th, 1916.] PROCEEDINGS. xxv 



A stream of coal-gas was passed through a tube immersed 

 in solid carbonic acid and ether, at — 79°C. This condensed 

 completely all the benzene, toluene and similar substances, but 

 allowed the whole of the ethylene to pass forward with the gas. 

 The luminosity of the flame of the issuing gas was very feeble 

 in comparison with that of the original gas. Measurements 

 carried out by Mr. W. Buckley at the Corporation Gas Works in 

 Rochdale Road, showed that a particular coal-gas lost 78 per 

 cent, of its illuminating power by this treatment. The benzene 

 hydrocarbons therefore contribute far more to the luminosity of 

 coal-gas flames than does ethylene, in spite of the fact that the 

 volume of ethylene present is usually three to five times the 

 volume of benzene vapour. 



A discussion on the President's Address — " On animal 

 symmetry and the differentiation of species" — was 



opened by Dr. W. M. Tattersall. 



Dr. Tattersall urged : — 



1. That radial symmetry is the direct outcome of a 

 sedentary habit and is more primitive than bilateral symmetry. 

 It appears in its most complete and primitive form in Coelen- 

 terates and Echinoderms, where it affects both external and in- 

 ternal structures. These groups of animals probably arose as 

 fixed forms before the appearance in the animal world of move- 

 ment by muscular effort. With the development of the latter 

 type of locomotion, radial symmetry was gradually eliminated 

 in favour of bilateral symmetry. All the higher groups of 

 animals are bilaterally symmetrical, and radial symmetry only 

 appears in those forms, such as sedentary W T orms, Polyzoa, 

 Tunicata, which have secondarily acquired a sedentary habit. 

 In such cases the radial symmetry is secondary and superficial, 

 only affecting the external organs. 



2. In those groups of fixed animals exhibiting primitive 

 radial symmetry, the Coelenterates, two types of variation are 

 found, (1) congenital variation, i.e., the variation of hereditary 

 characters, unaffected by the environment, and (2) vegetative 



