XII] OF THE FORAMINIFERA 869 



ConclvMon 



If we can comprehend and interpret on some such lines as these 

 the form and mode of growth of the foraminiferal shell we may also 

 begin to understand two striking features of the group, on the one 

 hand the large number of diverse types or famihes which exist 

 and the large number of species and varieties within each, and 

 on the other the persistence of forms which in many cases seem to 

 have undergone little change or none at all from the Cretaceous or 

 even frorri earlier periods to the present day. In few other groups, 

 perhaps only among the Radiolaria, do we seem to possess so nearly 

 complete a picture of all possible transitions between form and 

 form, and of the whole branching system of the evolutionary tree : 

 as though little or nothing of it had ever perished, and the whole 

 web of life, past and present, were as complete as ever. It leads 

 one to imagine that these shells have grown according to laws so 

 simple, so much in harmony with their material, with their environ- 

 ment, and with all the forces internal and external to which they 

 are exposed, that none is better than another and none fitter or less 

 fit to survive. It invites one also to contemplate. the possibility of 

 the lines of possible variation being here so narrow and determinate 

 that identical forms may have come independently into being again 

 and again. 



While we can trace in the most complete and beautiful manner 

 the passage of one form into another among these httle shells, and 

 ascribe them all at last (if we please) to a series which starts with the 

 simple sphere of Orhulina or with the amoeboid body of Astrorhiza, 

 the question stares us in the face whether this be an "evolution" 

 which we have any right to correlate with historic time. The 

 mathematician can trace one conic section into another, and " evolve " 

 for example, through innumerable graded ellipses, the circle from 

 the straight line: which tracing of continuous steps is a true 

 "evolution," though time has no part therein. It was after this 

 fashion that Hegel, and for that matter Aristotle himself, was an 



forms, said to be limited to Arctic and Antarctic waters, there is no principle of 

 geographical distribution to be discerned amongst them. A species found fossil 

 in New Britain turns up in the North Atlantic; a species described from the West 

 Indies is rediscovered at the ice- barrier of the Antarctic. 



