Gulick.] 
166 
[Jan. 2, 
General Meeting, January 2, 1889. 
The President, Prof. F. W. Putnam, in the chair. 
The following is an abstract of the first paper of the evening : — 
LESSONS IN THE THEORY OF DIVERGENT EVOLUTION 
DRAWN FROM THE DISTRIBUTION OF THE LAND 
SHELLS OF THE SANDWICH ISLANDS. 
BY REV. JOHN T. GULICK. 
I will first exhibit the typical forms of Achatinella Budii and 
fulgens , described by Dr. Newcomb, from the valley of Palolo, isl- 
and of Oahu. Though these species are found in the same valley 
and sometimes inhabit the same trees, they are distinguished from 
each other in a degree that is usually regarded as specific, as long 
as intergrades are not discovered. We find, however, that a com- 
plete series of tbe varieties and species collected in that valley, 
present a network of intergrading forms. Passing over the moun- 
tain ridge to the sheltered groves of the next valley on the north- 
west, less than a mile distant, w e are astonished to find that neither 
of the two species with which we commenced is present, and that 
the species most fully developed here are only sparsely represented 
by divergent varieties in the first valley. Passing over another 
ridge into the third valley, we find nearly all the arboreal species 
different from those of the first valley, though the vegetation and 
the habits of feeding are quite the same. 
Continuing our investigations in valleys ten and twenty miles 
distant, we find that the degree of divergence, for species of any 
one closely related group, is roughly measured by the distance by 
which the forms are separated, which is also the measure of the time 
and degree of the influences that have interfered with their free 
crossing. 
We also find that the species found in valleys twenty miles apart 
completely intergrade with each other through lines of species and 
varieties, found, for the most part, in valleys occupying the inter- 
mediate portions of the mountain range. From this fact, we learn 
that species are nothing more than strongly pronounced varieties. 
If freedom from intergrading is received as the necessary and suf- 
