414 ORIGINATIVE FACTORS IN EVOLUTION: 



barley, in strawberry and maize, in pomace-fly and potato- 

 beetle, in rat and in Man himself. Mutations may be induced 

 experimentally, as Professor Tower did with his potato- 

 beetles and as Mme. Henri recently did with the bacillus 

 of anthrax; or they may manifest themselves in wild nature 

 as in the black mutants of Peppered Moth and West Indian 

 Sugar-bird. The result may be a plus or a minus, a dominant 

 or a recessive or neither, pathological or normal. The muta- 

 tion may occur after crossing or in a pure race ; it may show 

 itself potentially before, during, or after fertilisation. In 

 short, there is nothing hard and fast about the origin or 

 nature of mutations : their common features are their brusque 

 appearance, their discontinuity with the parent stock, and 

 their capability of being transmitted intact to a certain 

 proportion of the offspring. 



The work of Dr. R. R. Gates on (Enothera lamarckiana is 

 of capital importance. It had been suggested that this species 

 might be a cultivated hybrid, and that its remarkable muta- 

 tions might be re-combinations of the Mendelian characters of 

 its parents. But it has been shown that (Enothera lamarck- 

 iana was in the 18th century at least a wild North 

 American species. Moreover, the brusque phenomena of 

 mutation occur not only in (E. lamarckiana, but in (E. 

 biennis, (E. grandiflora, and (E. muricata as well. 



Of particular interest in many of the mutations of (E. 

 lamarckiana is the fact that they affect several different 

 parts of the plant, including foliage, flowers, and habits. 

 The disturbance produced in the germ-plasm must be of a 

 fundamental character, it has manifold outcrops, as is sug- 

 gested by the names of the mutants gigas, lata, nanella, 

 rubricalyx, brevistylis, and so on. 



How does Dr. Gates interpret the germinal disturbances 



