28 



FRIENDS WORTH KNOWING. 



many species. Such changes may have happened any- 

 where, again and again, and thus the two halves of a com- 

 munity been divided. In succeeding centuries the mem- 

 bers of the parted sections may have diverged in their de- 



AN ALIEN IN THE CELLAR. 



velopment, until on this side of a mountain range, or desert, 

 or sea, we now find one set of species and on that side an- 

 other set, which belong to the same genera, and may in 

 some cases be proved, as well as surmised, to have had an 

 identical origin. 



