Oenothe?'a Oblonga. 339 



ohlonga mutants are almost always considerably more 

 numerous than the ruhrinervis ones. The observations 

 extend over six years (1895-1900), which is probably 

 only a small section of the whole mutation period. Never- 

 theless, the evidence seems to justify the conclusion that 

 the various new species arise from the parent form, at 

 any rate for a certain period, in definite and constant 

 proportions which vary from species to species. 



This consideration seems to me to lead to two im- 

 portant points. First, the probability that 0. Lamarckiana 

 is able to produce other mutations in even smaller pro- 

 portions, such as one in a million; in which case there 

 would not be much chance of their appearing in my cul- 

 tures. In other words if one could make the whole ex- 

 periment ten or a hundred times as extensive, one would 

 be very likely to get more mutations and amongst them, 

 possibly, some better than those which have already ap- 

 peared. 0. laevifoUa and 0. hrcvistylis might then arise 

 again. 



The second point relates to the causes of these pro- 

 portions. Is it possible to interfere with and alter the 

 "mutation coefficients" ? Is there any hope of increasing 

 the proportion of the rarer species?^ And when a method 

 of doing this will be invented will it be possible to obtain 

 mutations which are at present presumably too rare to 

 appear ? 



An experimental study of the process of mutation 

 during the mutation period may even put into our hands 

 the power to bring about the inception of such a period ; 

 or in other words the power to make an immutable spe- 

 cies mutable. 



^ See the case in § < (on page 264) where, as a result of defective 

 germination the proportion of mutants arose to 40 %. 



