208 Willis . — and Area. 
other phenomenon described above, and seems to me completely to answer 
Mr. Tate Regan. 
Mr. Tate Regan then &ent on to emphasize the importance of sterility 
and of isolation in evolution—points to which there will be few dissentients. 
It may be pointed out that the large mutations postulated by my supposi- 
Fig. 4. Hollow curves exhibited by the grouping into sizes of the genera in ten British Floras, 
1782-1908. 
tions (11, p. 215) will be much more likely to be mutually sterile with their 
ancestors than would smaller ones. 
Pinally Mr. Tate Regan objected to Age and Area because it did not 
explain adaptation. This, however, no theory since the older theories of 
Darwin and Lamarck has attempted to do. Personally I do not think that 
adaptation is nearly so well marked as is often supposed (cf. 6), and it has 
often been pointed out, e. g. by de Vries on p. 224 in my book, and by 
