230 PROBLEMS OF GENETICS 



careful tests, however, he withdrew this opinion. It proved 

 that both individual flies and individual groups of flies, both of 

 those bred in the light and of those bred in the dark, differed 

 greatly in their reactions, which were measured by counting the 

 time that it took for a fly to travel to the light end of a covered 

 tube, various sources of error being eliminated. He found further 

 that these differences of behaviour were not inherited in any 

 simple way, but he is disposed to attribute them to accidental 

 differences in the nature of the food, an account which seems 

 probable enough. 17 



In several recent publications Blaringhem 18 has described 

 the origin of many abnormal forms of plants, especially of maize, 

 which he attributes to various mutilations practised upon the 

 parents. Respecting these the same difficulty which has been 

 expressed in other cases reappears, that before drawing any 

 conclusion as to the value of such evidence we require to know 

 that the plants treated belong to a really pure line, which if 

 left to nature in the ordinary circumstances of its life in that 

 locality would have had normal offspring. Abnormalities abound 

 in the experience of everyone who examines pans of seedlings 

 of almost any species of plant, and in maize they are well known 

 to be exceptionally common. Some of those which we meet 

 with when we attempt to ripen maize in this country are very 

 similar to those which Blaringhem describes, consisting in ir- 

 regularities in the distribution of the sexes, in the shapes of the 

 panicles, etc. Many of these are doubtless imperfections of 

 development, due to the dullness of our climate, but others are 

 presumably genetic and would recur in the offspring however 

 treated. If some one working in a climate where maize could 

 be raised in perfection would repeat these experiments, and show 

 that a strain which was thoroughly reliable and normal in its 

 genetic behaviour did, after mutilation, throw the miscellaneous 

 types observed by Blaringhem, that would be evidence at least 

 that the development of the seed could be so influenced by 

 injury to the parental tissues that its properties were changed. 



17 Payne, Fernandus, Biol. Bull, XVIII, 1910, p. 188, and ibid., XXI, 1911, 

 p. 297. 



18 See especially, Mutation et Traumatismes, Paris, Felix Alcan, 1908. 



