284 TOWARDS THE HUMAN FORM 



the Arctic region was still about 12 C, according to 

 Oswald Heer. At Spitzbergen there grew side by side with 

 Osmundas, Horsetails and Taxodiums — Poplars, Plane-trees, 

 Walnuts, Elms, Hazels, Hamamelidacere, Alders,. Magnolias, 

 Lime-trees, Viburnum, Catalpas, etc., and to these were 

 added in Greenland, Willows, Birches, Myrica, Beeches, 

 Maples, Holly, Ash, Hawthorns, Plum-trees, Black Alder, 

 Rhubarb, Ivy, Cornaceae, and even the Grape-vine. The 

 relative lowering of the temperature during the Cretaceous 

 Period, however, is sharply indicated by the absence of Palms 

 from these regions. Fewer species appeared even in Europe. 



Although these questions have been discussed before 

 (pp. 28, 51), from another point of view, it was necessary to 

 recall the facts here in greater detail to render intelligible 

 the relation they bear to the various fauna that succeed one 

 another. The Nummulites appear to be a transformation of 

 an older genus of Foraminifera, the still extant Operculina, 

 to which should be related the Assilinas with their less 

 complete spirals. The Nummulites are so numerous in 

 that it has been possible to use them to determine the 

 lines of the sea-coast, and on account of their widespread 

 distribution they have furnished us with the best method of 

 studying the deposits of this age and their development. 

 The different types of our present Invertebrates were already 

 determined, and though their species, dating like coins the 

 age of the various strata, have a great interest for geologists ; 

 though it is often possible to follow their transformations 

 through a series of layers (as in the case of certain Cerithidse) 

 and to bring thereby supplementary, but not indispensable 

 support to the doctrine of evolution ; yet they are only 

 of secondary importance from the point of view that we 

 are considering here. What we seek are the causes which 

 lead to the formation of the principle organic types, and 

 the laws that have determined their evolution. We 

 cannot enter here into a discussion of the infinitely varied 

 accidents — often, indeed, quite beyond our ken — that have 

 determined the characteristics of species. 



Among the Vertebrates we saw different types of Fishes, 

 Batrachians, and Reptiles appear, evolve, and very often 

 disappear. From the Cretaceous up to the time when they 

 appear to be almost as varied as they are at the present day, 



