XII] OF THE FORAMINIFERA 607 



Conclusion. 



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, 

 namely, on the one hand the large number of diverse types or 

 families 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 Uttle change or none at all 

 from the Cretaceous or even from 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 h9,rmony 

 with their material, with their environment, 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 Uttle shells, 

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

 with the simple sphere of Orbulina 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 con- 

 tinuous 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 evolutionist— to whom evolution was 



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. 



