SECTIONAL TRANSACTIONS.— C, D. 329 



illustrate the importance of correlating palseobotanical data with geological data on 

 the trend of mountain chains, which may have served as highways of migration. 



In the Lower Carboniferous there were no well-defined botanical provinces, but 

 the Upper Carboniferous flora of the northern hemisphere is different from that of 

 the south, though the differences have been exaggerated, tlie northern flora being 

 much richer and more varied than that of the south. The evolution of the Glossop- 

 teris flora was in the main governed by climatic factors. 



SECTION D— ZOOLOGY. 



(For reference to the publication elsewhere of communications entered in the 

 following list of transactions, see p. 428.) 



CAPE TOWN. 

 Tuesday, July 23. 

 Joint Meeting with Section I (q.v.) on Experimental Biology. 



Wednesday, July 24. 



Prof. 0. Abel. — Ideas on the Causes of Degeneration of Species. 



The struggle of life produces adaptations in the individual which may be 

 advantageous or disadvantageous. It is difficult to recognise the latter among 

 living forms, but the toe-reduction in the Ungulates described by Kowalesky and 

 the carnassial teeth (' break-scissors ') of the Hysenodontidae and Oxysenidaa are fossil 

 examples. 



Palaeontology clearly shows that the first step in the way of adaptation to a special 

 environment or function is inherited and becomes a determining factor in further 

 evolution. Such orthogenetic evolution of a disadvantageous adaptation would not 

 be called Degeneration. In the ordinary course of variation or of development some 

 individuals are ' defective ' or ' degenerated.' As a rule they will not affect the 

 adaptive or physiological value of the individuals of the next generation, because they 

 wiU not reach maturity. An example is the stunted or famine form of the Stag Beetle 

 (Roe Beetle) due to the lack of larval food in the Slavonian forests. 



Degeneration in regard to Morpliological characters manifests itself in the 

 insufficiency of certain organs either in part or whole as compared with the sufficiency 

 of the same organs in individuals of good health. In the Physiological sense the 

 degenerated state of an individual manifests itself in the insufficiency of its reaction 

 to the influences of its su<;roundings in comparison with the normal individual. 



In famine or stunted forms the immediate cause is shortness of food. Opposite 

 conditions may bring about the same result, as in the case of preserved game, where 

 the survival and breeding of the feeble individuals gradually deteriorates the whole 

 stock. The consequences of an easier struggle for Ufe must always be the survival 

 of more individuals and a wider variation, for the species which gains the optimum 

 of life-surroundings seems to enter upon a flourishing period of evolution, which, 

 however, is not of any phylogenetic value. 



Unfortunately the increase of individuals in life-optimum conditions includes 

 defective ones as well as those in good health, and natural selection is diminished at 

 the same time. So the percentage of defective ones will increase until it becomes 

 too great for the species as a whole. Natural Selection is therefore of enormous 

 importance for the conservation of the species, and the history of a species, whose 

 life-surroundings change from a hard struggle to a life-optimum, must, after a period 

 of flourishing, end in extinction. 



The foregoing theoretical reflections receive abundant support from the many 

 thousand fossil bones of the Cave-bear (Vrsiis spelceus) in the Pleistocene deposits of 

 the great Dragon Cave near to Mixnitz in Austria. There the ancestral form 

 (V . deningeri) shows little variation, no healed injuries nor disease; while in the 

 upper deposits the fossils show as wide a variation as the domestic dog, with severe 

 fractures healed, co-ossification of the vertebrae, rickets in old specimens, serious 



