292 



has arisen, and the day when these so-called new countries 

 cease to attract the vigorous life of Europe will be the signal 

 for their lagging behind in the race of life and progress. 



In conclusion I trust I may be allowed to express the hope 

 that some at least of my hearers will find themselves in sym- 

 pathy with the lines of thought I have endeavoured to demon- 

 strate, and that their co-operation will materially advance our 

 knowledge of Entomology, a study which in some of its depart- 

 ments is still in the analytical stage and has scarcely yet entered 

 on the synthetical. 



The immense numbers of new species that are so unceasingly 

 discovered, and must be examined, described, and classified, 

 leave little opportunity for those so engaged to consider the 

 great principles underlying the study, or to formulate the laws 

 governing its phenomena in the insect world, but there are doubtless 

 some whose inclinations lead them to investigate the laws of 

 nature as exemplified in insects, and it is more especially to 

 them I commend the study of Dominance and its correlation 

 with Evolution, Phylogeny, and Distribution. 



EXPLANATION OF PLATES VI— X. 



Fig. I. — Map illustrating the geographical distribution of the Pentatcsnia, 

 the most dominant group of Helicidœ, showing their aggre- 

 gation in and about the chief evolutionary area, which is 

 indicated by the darkest shade. 



Fig. 2. — Map illustrating the expulsion of the sub-dominant genera, 

 Helicigona, Helicella, and Helicodonta^ from the chief evolu- 

 tionary region, by their more advanced successors, and showing 

 the initiation of discontinuity of distribution. 



Fig. 3. — Geographical distribution of Helix pomatia, one of the most 

 dominant species, showing the line of its eastward advance 

 through the area between the southern boundary of the 

 Boreal province of Milachevitch and the northern boundary 

 of the Pontic region of Drouet, which are indicated by shaded 

 lines. 



Fig. 4. — Map of the approximate routes of the dispersal of life from the 

 chief evolutionary area in North Central Europe. 

 The stronger waves broadly indicate the main lines of migration, 

 the finer ripples the relative slowness of the advance. 



