president's address. — SECTION D. 261 



which light was exchaded exhibited the flattening to the full extent, 

 although it did not, of course, develop chlorophyll. On the other 

 hand, the thickening of the cells, especially of the exodermis, was 

 noticeably less than in the light. It should, of course, be clearly 

 recognised that this experiment proves only the persistence of an 

 acquired character when the part exhibiting it was grown in conditions 

 the reverse of those in which the character was originally acquired. 

 There is not the evidence of heredity that actual seedlings might or 

 might not give. 



In the Auckland Islands Metrosideros lucida, which forms the bulk 

 of the forest, and Olearia LyaUii, have adapted themselves to their 

 wind-swept environment by becoming more or less prostrate, the trunk 

 becoming horizontal and being partly supported by its branches. 

 Cockayne ("Sub- Antarctic Islands of New Zealand," p. 194) points out 

 that seedlings of Olearia Lyallii growing in sheltered spots in the forest 

 frequently present this habit. The shelter in some of these spots 

 is very effective indeed, and it is difficult to regard this as anything but 

 a case of inheritance of an adaptive character acquired by the parent. 



The work of Tower and MacDougal shows clearly that the germ 

 plasm is susceptible of direct modification by environment, although 

 the soma in which it is lodged may remain unmodified. The work of 

 Castle and Phillips shows tliat, in the conditions of their experiments, 

 the soma in which the germ plasm was lodged exerted no influence 

 that could produce modification. Are we then to assume that modi- 

 fications in the soma can never affect the germ plasm ? It seems 

 difficult to admit that the soma, which is in the higher organisms, an 

 absolutely essential part of the environment, can exert no modifying 

 influence. There is the difficulty felt by Eigemann and others in account- 

 ing for the facts as we find them, if somatogenic modifications may 

 never become blastogenic ; there are the clear cases we have mentioned 

 in which it the modification has arisen in the soma, and has resulted 

 a modification of the germ plasm and become transmitted. It seems 

 to me that all that can be conceded is that modifications certainly arise 

 by action of environment on the germ plasm, while there is much 

 reason to believe that the environmental factor that acts immediately 

 on the germ plasm is in many cases the soma, itself modified or becoming 

 modified as an expression of its response to external conditions. But 

 between immediate action of extra-somatic environment on the germ 

 plasm, and mediate action through a soma modified or in course of 

 modification, there will probably be found in the majority of cases a 

 wide difference. In the first instance the action may be sudden, and 

 the results clearly expressed in a generation. In the second instance, 

 where somatogenic modifications becomes blastogenic, the two kinds of 

 modification may go on slowly and almost fari passu. In the former 

 instance we have mutations ; in the latter, generally, but perhaps not 



