196 WHAT IS LIFE ? 



kangaroos, were the only mammals, and were therefore 

 the most highly organized creatures existing in these 

 formations. Certain types were akin to the American 

 opossum. 



Nevertheless, notice how Nature keeps on progressing 

 from the simple to the complex, from the complex to 

 the more complex, from high to higher structures. 



The Jurassic formations are found in Britain, France, 

 Germany, Sweden, Russia, North America, Asia, and 

 Australia. 



Lying over and deposited later, upon the Jurassic 

 rocks, are a set of strata, called by geologists the 

 .Cretaceous rocks. Part of this system is well marked 

 in England, we call the rock, chalk. Plant life is of 

 great interest, as we have the first indications of the 

 higher vegetation living to-day. When these organisms 

 flourished, the climate of Europe was probably 

 warmer than at present. Now remains are found of 

 the oak, willow, beech, plane, poplar, maple, hickory, 

 fig, tulip-tree, sassafras, laurel, cinnamon, buckthorn, 

 together with ferns, American palms, &c. 



But the Chalk is exceptionally interesting. It 

 largely consists of perfect but minute calcareous 

 shells foraminifera. The creatures which secreted 

 these shells from the carbonate of lime, which was 

 held in solution in these ancient seas, consisted of 

 masses of molecules- attracted to each other, and we 

 call these masses protoplasm. Marvellously wonder- 

 ful are the forms this protoplasm takes ; occupying 

 the shell, it radiates through minute orifices in it 

 like so many fine hairs in all directions. The object 

 of these processes is to collect food existing in the 

 water. Besides these minute shells there are larger 



