HYATT: GENEALOGY OF ACHATINELLID^E. 387 



island to another. In other words genetic lines -of descent 

 can be traced in the shells throughout the islands beginning 

 with Kauai, the oldest geologically, and following the whole 

 chain to the southeast until one arrives at the most recent 

 island of the archipelago, Hawaii. 



This entire picture of variability appears therefore like 

 those that have taken place in past geologic times, and known 

 to occur when an animal type of primitive form finds itself 

 in a free field, either an uninhabited locality as Kauai must 

 have been when the first ground shells reached there, or a 

 new and unoccupied station, as the bushes and trees of Oahu 

 were, when the ground-shells or their modified descendants be- 

 gan to creep up on their stems. 



The opportunities for expansion by the evolution of varied 

 types were certainly afforded by the surroundings, and it 

 must be acknowledged that this divergence into new groups 

 takes place along the open ways of migration. This is dif- 

 ficult to account for by any hypothesis that does not consider 

 the primitive Amastras as a plastic type the structure of 

 which was capable of being modified so as to occupy all the 

 available environments afforded by these islands. If this be 

 so, the various successful types evolved in distinct genera 

 certainly appear to have arisen as secondary modifications, 

 which could not have come into existence if the new fields 

 and stations had been already occupied or were inaccessible. 

 The variations are, as a rule, obviously still coincident with 

 and limited to the locations and islands in which they origin- 

 ated, and this correlation cannot be accounted for unless we 

 grant a causal relation between the surroundings and their 

 faunas. 



PART II : REMARKS UPON RELATIONSHIPS BETWEEN GENERA. 



[The more or less disconnected notes constituting the second part of 

 this paper must be of interest to students of the Achatinellidce. When 

 death overcame him, Professor Hyatt had all but completed his prepara- 

 tions to visit the Hawaiian Islands, the funds for such an expedition 

 having been provided by Mrs. Jennie Arms Sheldon. In certain cases, 

 doubtless, his ideas of the actual relationships between genera would 

 have been somewhat modified and all would have been amplified and 

 rendered more precise through a study of the animals in the field. 



