NOTES ON SOME PROBLEMS OF ADAPTATION. 



249 



Our Chiton tuberculatus were secured from two well-contrasted 

 situations (cf. Crozier, 1918) : an exposed ocean beach on the 

 south shore of Bermuda (here referred to as "South Shore"), 

 and the shores of an enclosed sound, Great Sound. In Fig. 2 the 

 mean ctenidial frequency for each size class is contrasted for these 

 two locations. Clearly there is no great difference between the 



100 



90 



so 



r> 





 LI 

 o 



70 

 c 



n 

 <u 



South Shore 

 O Great Sound 



I I 



I I I I 



I 2 3 4 5 6 7 8 9 10 II 12 13 -run. 

 Lengtn of valve 4 



FIG. 2. 



two sets of observations, though the lower number of ctenidia in 

 the younger animals from the South Shore may perhaps prove 

 significant. 



4. Is it possible that the asymmetry of gasteropods is in some 

 manner foreshadowed among the chitons? The two liver-lobes of 

 young chitons are at first symmetrical, but later the right lobe 

 becomes the smaller and is pushed anteriorly (Pelseneer, 1906, 



