35 8 GEOLOGICAL BIOLOGY. 



amount of effective use for the least expense of energy or 

 material; (b) from the point of view of ontogenetic growth, 

 that is, the natural order by which the structure is produced 

 in the normal growth of an individual organism ; and (c) 

 from the point of view of historical sequence. 



But this is not a case of the survival of the fittest, it is 

 the evolution of the fittest, and, from this point of view, too, 

 it is not the fittest that survives; for of these ancient forms it 

 is the Nautilus, and not the Ammonite, that survives; but of 

 the order of initiation there is no mistake the Ammonite does 

 not appear before the Nautiloid; and the sequence Goniatite, 

 Ceratite, Ammonite is not reversed, but is the order which 

 the structure would suggest. The general law of survival 

 of the fittest is exhibited in the general dominance of one 

 type over another, but a structure once developed may persist 

 entirely beyond the period of its relative importance or rela- 

 tive stage of perfection, as is wonderfully exhibited in the 

 Lingulas of the modern sea, which are traceable back to the 

 Cambrian period through a line of ancestry that was very 

 highly modified in many parallel lines, of which only Lingula 

 survives. 



