70 DIVERGENCE AND PARALLELISM 



we ascend higher in the scale of nature we find 

 that the co-ordinating mechanism of the animal 

 body keeps pace with the rest of the organisation, 

 and the leading members of the several phyla or 

 branches of the animal kingdom become ever 

 farther removed from each other and from what 



FIG. 2. Diagram of phyletic divergence and parallelism. 



we may designate vaguely as their common 

 starting-point. Thus the highest Mollusca, the 

 Cephalopoda (squids, octopods, cuttle-fishes, and 

 Nautilus), which are characterised by a high 

 degree of cephalisation or concentration and 



