PREFACE. Vll 



application of biological science not only to investigate and 

 map out these two paths of organic progress, but to illuminate 

 them. Hence we have attempted to indicate the application of 

 the general organic survey, which has been our main theme, to 

 such questions as those of human population and progress, 

 although here, more even than elsewhere, our treatment can be 

 at best only suggestive, not exhaustive. While limits of space 

 have made it impossible to give the botanical side of our sub- 

 ject its proportionate share of attention, our illustrations of the 

 essential facts are sufficient to show the parallehsm of the 

 reproductive processes throughout nature. 



It remains to express our thanks to Professor F. Jeffrey 

 Bell for some valuable suggestions while the work was passing 

 through the press ; to Mr G. F. Scott-Elliot for assistance in 

 summarising certain portions of the literature; and to our 

 engravers, Messrs Harry S. Percy, F. V. M'Combie, and G. 

 A. Morison, especially to the first-named, who has executed 

 the great majority of our illustrations with much care and skill. 



PATRICK GEDDES. 



J. ARTHUR THOMSON. 



