MancJiester Memoirs, Vol. lix, (1915), No. 4. 9 



The existence of such a correlation was further shown 

 in the following way. The ratios -„ and -. obtained for 



each shell were plotted against one another ~ ratios being 



„. ~ 1 • , ■■• ., • r 1 • Length 



risr. 4. — Curves showing the distribution of the ratios -=• — -r— 



* ^ b Depth 



among iooo individuals of Reticularia lineata, the 



individuals being divided into three groups according to 



size. 



Dot-dash line = individuals with length of 0*15 — 0*45 inch. 

 Continuous line — individuals with length of 0*45 — 075 inch. 

 Broken line = individuals with length of 0*75 — 1*05 inch. 



i*9 i-8 17 i-6 i'5 1-4 1*3 1*2 i'i 



■^ — f Length 



Depth 



taken as abscissae and ~ ratios as ordinates. Each shell 



is thus represented on the graph by a point. The graph 

 field was now divided up into small squares by drawing 



