Manchester Memoirs, Vol. lix. (191 5), No. 4. 7 



The three curves are simply the components of the 

 distribution curve in Fig. 1. It will be seen from a 

 consideration of Fig. 3, that each of the three curves is 



/-a 1 1 *• -i r , • Length 



Fig. %. — Lurves showing the distribution of the ratios -=r — -r-r 



6 J b Breadth 



among ioco individuals of Reticularia /ineala, the indi- 

 viduals being divided into three groups according to size. 



Dot-dash line = individuals with length of 0T5 — 0*45 inch. 



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



Broken line = individuals with length of 075 — 1*05 inch. 



140 



120 — 



100 



itself a very regular simple variation curve: separately 

 therefore, each confirms the fact deduced from Fig. 1 that 

 one species only is under consideration. 



