Seven parts, i. e. height (H・S) and weight (W・S) of the shell, total body weight (I・W), fresh (B・W・f) and dry (B・W・d) weight of the soft part, water content (W・C・B) of the soft part, and that contained in the mantle cavity (W・M・C) were measured comparatively and considered on the basis of the equation Y=kX^a of relative growth. All curves of shell-height growth are logarithmic against other six parts mentioned, indicating the faster growth of the former. The relations between growths of all other parts except the height of shell, however, are completely isometric. This shows that the rates of growth of all these parts are almost equal to one another. There is a break in the growth curve of shell-height at the point of value of about 15 mm. The most important component in the growth of the total body weight of the pond-snail lies in the water of soft part of body, the water in the mantle cavity coming next. The shell weight and the dry weight of the soft part of body both concern to it in relatively small extent.

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