xxvi Proceedings. [January 25th, 1916. 



variation, due to the direct action of the environment. Con- 

 genital variation has not been proved to be more intensive 

 among radially symmetrical animals than among bilaterally 

 symmetrical forms. This type of variation alone is of im- 

 portance in the evolution of discontinuous specific groups. 

 Vegetative variation is characteristic of fixed forms and is the 

 direct result of a sedentary life. It is a measure of the adapta- 

 bility of the animal to its environment, and is practically 

 unknown in free-living bilaterally symmetrical animals. It is 

 of no value in the evolution of discontinuous specific groups. 

 There is no correlation between radial symmetry and vegetative 

 variation, except in so far as both are the result of a fixed habit 

 of life. 



3. Systematic Zoologists have hitherto attempted to dis- 

 tinguish discontinuous specific groups among radially sym- 

 metrical animals on characters which are the result of vegetative 

 variation, and have found difficulty in doing so satisfactorily. 

 This is, however, no evidence that such groups do not exist. 

 A study of those parts of radially symmetrical animals which 

 are less liable to the effects of the environment and therefore 

 more constant in character will probably yield results of im- 

 portance for the discrimination of species. Such work has 

 already yielded encouraging results among Corals, one of the 

 most variable groups of radially symmetrical animals. Until 

 more such work has been done and the results examined it is 

 premature to deny the existence of discontinuous specific 

 groups in radially symmetrical animals. 



Sir Henry Miers, M.A., D.Sc, F.R.S., called attention to 

 the radical difference between the symmetry of an organism 

 and that of a crystal. Individual crystals display bilateral or 

 multilateral symmetry, and a group of crystals may display 

 radial symmetry but always of a two-, three-, four-, or six-fold 

 character ; and this is now known to be a consequence of the 

 homogeneity of a crystal. He asked whether anything is known 

 of the cause which determines the number of repetitions in 

 a normal specimen of a radially symmetrical organism. 



