360 EEV. J. T. QUIiICK ON 



Similar Facts in other Fields, 

 Many of the facts embodied in these eight propositions must 

 have been observed wherever naturalists have studied the 

 geographical distribution of tlie varieties and species of poly- 

 morphic genera; but in the distribution of the AcTiatinelUncs 

 there are features of peculiar interest arising from the fact that 

 the powers of migration possessed by the species of the sur- 

 rounding environment are very much greater than those possessed 

 by the Acliattnellce. Through this circumstance a comparatively 

 uniform environment is produced in which the effects of Inde- 

 pendent Greneration unmodified by the effects of changed 

 environment may be observed. The remarkable facts of dis- 

 tribution which we have on the island of Oahu are found in 

 other parts of the Sandwich Islands, wherever this family occurs. 

 I am also fully convinced that, in other parts of tlie world, 

 wherever one genus or family of very low powders of migration 

 is surrounded by a body of plant and animal forms possessing 

 much higher powers of migration, these similar facts will present 

 themselves whenever investigation is made. 



The distribucion of land-mollusks belonging to the genus 

 Partida found on the Society Islands presents similar features. 

 The island of Eeiatea, which is but 14 miles in length and 3 or 

 4 miles in breadth, is the home of about 30 species and varieties, 

 most of which are confined to areas only a few square miles in 

 extent. I am not informed as to the distribution of the vegetation 

 on which these species feed, but there is no reason to suppose 

 they occupy limited districts corresponding to those occupied 

 by the difterent species of Partula. 



DivEE&ENCE IN Insects. 

 The dependence of divergence on some form of Segregation is 

 most clearly exemplified in insects, and though my studies are 

 but limited in that field, I shall refer to a fe^v cases, which may 

 serve to direct attention to a class of facts of the highest interest 

 not only to Entomology but to general Biology. 



DiVER&ENCE IN THE SPECIES OJ? THE LePIDOPTEEOTJS GeNEEA 



Erynnis {Famphila) and Tlianaos {Nisoniades) . 

 These two genera of small North-American butterflies are 

 worthy of the special attention of those who are studying the 



