684- REPORT— 1903. 



As Trembley showed many years ago, a Hydra can be cut into many pieces, and 

 each by the regeneration of the parts that are missing will give rise to a complete 

 individual. The Earthworm can, when cut in half, regenerate a now tail but not 

 a new head region. An Arthropod dies when cut in half, but has the power of 

 regenerating new appendages in place of those that are lost. But in Vertebrates 

 there is very little power of regenerating new appendages, and the general powers 

 of regenerating new parts are reduced to a minimum. 



Now, whether the loss in the plasticity of characters was the cause of the loss 

 in the power of regeneration of lost parts, or the loss in the powers of regeneration 

 was the cause of the loss of plasticity, is a problem upon which I do not feel we are 

 competent to express a definite opinion ; but that the two series of phenomena are 

 intimately associated is, I believe, a generalisation that is worth a good deal of 

 further thought and study. 



In Vertebrates, however, although the power of regeneration of lost parts is at a 

 minimum, it is not by any means entirely wanting. The muscles, nerves, epithelia, 

 and other tissues, are able to repair injuries caused by accident and disease. 

 And similarly, although the power of response of various organs to the changes 

 of external conditions in Vertebrates is very much diminished as compared with 

 that in the lower groups of the animal kingdom, it still remains in an appreciable 

 degree. Whether the curves of variation of the so-called fluctuating characters of 

 Vertebrates represent simplj' or solely the influence of the environment on the 

 organism cannot at present be determined with any degree of certainty ; but it 

 appears to me that zoological evidence, confirmed as it is in such a remarkable 

 way by the recent researches of the botanists, points very strongly to the 

 conclusion that the major part of each such curve is, after all, but an expression of 

 the influence of the environment. In venturing to put before you these considera- 

 tions, I am quite conscious of the vastness and complexity of the problems involved 

 and of the many omissions and imperfections which a short Address of this kind 

 must contain. Not the least of these omissions is that of any reference to the 

 distinction that might be drawn between continuous and discontinuous variations 

 in the simpler forms of life. This is a matter, however, which involves so many 

 interesting and important questions that I have felt it to be beyond the scope of 

 my Address to-day. 



We are still in need of further systematic knowledge of the widely distributed 

 ppecies of Coelenterates ; we want to be able to form a more definite opinion than 

 we can at present upon the value of specific distinctions, and we need still further 

 observations and descriptions of the phenomena of irregular facies, abnormal 

 growths, and meristic variations. But more important still is the need of further 

 researches in the field of experimental morphology. 



When we have accumulated further knowledge on these lines in a group of 

 animals such as the Coelenterata, of relative simple organisation, we shall be in a 

 better position than we are now to deal with the problems of heredity and 

 variation in the far more complicated groups of Arthropoda and Vertebrates. 



THURSDAY, SEPTEMBER 10. 



The following Papers and Reports were read : — 



1. Some Results on the Morphology and Development of Recent and 

 Fossil Corals.^ By J. E. Duerden, Ph.I)., A.R.C.Sc. (Loud.) 



The paper gave a brief account of the results obtained from a morphological 

 study of the polyps of over thirty species of We.st Indian corals collected by the 

 author while Curator of the Museum, Jamaica ; also a preliminary note upon the 

 relationships of the extinct Tetracoralla to living Zoanthids. 



' Has appeared in Mem. of Nat. Acad, nf Sciences, Washington, vol. viii. 



