Gross Anatomy of Campeloma. 493 
than are those in the rear portion of the sac. All the young in 
the anterior portion possess shells. The shell of the young at 
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PELEELEEEEE TITS I 
FIG. 2, 
this stage is devoid of colored epidermis, is crystalline white, and 
possesses from 2 to 2} complete whorls. The apex is very short 
and blunt, the first whorl being nearly uniform in diameter 
throughout its length, while the body whorl is very large, com- 
prising fully nine-tenths the entire bulk of the shell. The darker 
tentacles and the black eyes at their outer base are readily seen 
through the substance of the shell. The average dimensions of a 
dozen or more young examined were, for length 3.5 mm., for — 
diameter 2.96 mm, The embryonic whorls never, so far as exper- 
lence goes with mature specimens with completely preserved 
apices, acquire the characteristic green epidermal coloring. : 
