i 



neck of the giraffe was caused by both these factors. 

 Weismann, on the other hand, believes in " the all-sufl&ciency of 

 natural selection," and holds that peculiarities acquired after 

 birth are not inherited. The lecturer then explained the theories 

 as to heredity of Darwin and Weismann in detail, and claimed 

 that Francis Gratton had anticipated Weismann in his doubt of 

 the doctrine of inheritance of acquired qualities. The real 

 question turned on whether the effects of use and disuse were 

 inherited. Herbert Spencer went so far as to say " either there 

 has been inheritance of acquired characters, or there has been no 

 evolution " ; but he stood almost alone in this view. The 

 examples quoted by Spencer were then discussed. Doubt was 

 thrown on the statement that the modern human jaw had 

 diminished in size. The blindness of crabs in the mammoth caves 

 of Kentucky was explicable on the theory of cessation of natural 

 selection (panmixia) rather than as the inherited result of disuse. 

 The special apparatus of the woodpecker for extracting maggots 

 from tree holes was similarly explicable. 

 Use and Disuse. 

 It was to be remembered that nature was in no hurry, and 

 that the production of varieties had often extended over vast 

 periods of time. There was little direct evidence of the 

 inheritance of the effects of use and disase. The favourable 

 coincidences were remembered, unfavourable cases were over- 

 looked. The Chinese female children had had their feet cramped 

 and confined from birth for a large number of generations, but 

 there was no evidence that they were now born with smaller feet 

 thau other children. The case of neuter insects appeared to 

 exclude the influence of inheritance of acquired powers. They 

 were sterile and yet varied again considerably ; some again be- 

 coming atrophied, &c. It might be imagined, from the pre- 

 ceding remarks, that the eavironment of the individual had no 

 effects upon the fortunes of the race. Weismann, however, agreed 

 that conditions affecting the embryo might influence its develop- 

 ment. Mr. Merrifield's experiment on butterflies showed that 

 low temperatures applied in the pupal stage produced a deepen- 

 ing of the ground colour and an extension of the dark 

 markings ; while high temperetures had an opposite effect. 

 The effect of environment was also seen in bacteria, which were 

 unicellular organisms. The anthrax bacillus could be deprived 

 of some of its virulency by growing it in a particular way. 

 Vaccine lymph was probably simply small-pox-lymph essentially 

 modified by being grown in the tissues of the cow. There could 



