﻿SNAIL HOST OF ORIENTAL LUNG FLUILE — ABBOTT 



105 



COLONY MEANS 



HISTOGRAMS 



Figure 43. — Means and histograms of population samples from Guam Island (see p. 103 



for explanation). 



flow of these streams at various seasons were made. It would be 

 interesting to mark and to transplant snails from, say, Agana Spring 

 to Umatac Kiver to see if final growth conformed with the latter 

 environment. A reciprocal transplant would be equally illuminating. 

 Effect of erosion on shell length. — Whenever the water of the 

 habitat of fresh-water mollusks becomes acid, there is apt to be a 



