ORGANIC DEPENDENCE AND DISEASE 23 



perately and in easy surrender it has exceeded its first pur- 

 pose and finally walled up its owners against a fighting 

 chance for improvement. 



STABILIZATION, LONGEVITY AND DISSOLUTION 



Over and over again in the history of the earth we find 

 the evidence of a methuselan stability among living crea- 

 tures, usually shown in definite species but sometimes per- 

 meating an entire assemblage or fauna. Ruedemann has 

 shown in great detail the extraordinary number of conser- 

 vative types or "radicles" which have been perpetuated 

 through the geological ages. It is a remarkable role of de- 

 linquents. 1 



Such illustrations as these will serve : There are the pro- 

 toplasmic Foraminifera which appeared in the Ordovician 

 and Silurian and have kept their generic characters over 

 the lapse of millions of years, to the best of our knowledge, 

 into the present seas (Saccamina, Lagena, Nodosaria). The 

 brachiopod Lingula lives abundantly in the existing seas; 

 its life began in the early Ordovician, and though students 

 of this group believe they see some divergence in structure 

 between the ancient and the existing Lingula, yet the type 

 is but slightly altered and the line is unbroken over this 

 enormous range of the ages. The brachiopod Crania has 

 had a like career, and another brachiopod species, Leptaena 

 rhomboidalis appeared in the Ordovician seas and con- 

 tinued as a specific type through the Silurian, the Devonian 

 and Carboniferous, thus caught in the world-wide conti- 

 nental disturbances which brought to its close the long 

 Paleozoic era. It varied indeed within limitations but re- 

 tained its essential specific characters without dissolution 

 for a period probably ten thousand times as long as the 



i R. Ruedemann. "Paleontology of Arrested Evolution"; Presidential ad- 

 dress before The Paleontologieal Society. (N. T. State Mus. Bui. 196, 1916, 

 pp. 107-34.) 



