GOD IN NATURE I 93 



trace of the subsequent structures, to produce this 

 wonderful framework. Can anyone who studies such 

 an organism summon faith enough in atoms and 

 forces to believe that their insensate action is the sole 

 cause of its being ? But our Euplectella aspergillum 

 is only one of several species, and there are other 

 genera more or less resembling it, most of them in 

 habiting the depths of the sea. All of these build 

 up silicious skeletons on what is termed the hex- 

 actinellid plan, but with differences of detail perfectly 

 constant in each species, though we cannot trace these 

 differences to anything corresponding in the animals, 

 nor can we assign them to any property of silica, 

 since the material of the spicules is in a colloidal or 

 uncrystalline state, and the forms are quite different 

 from the crystalline forms of silica. 



These hexactinellid sponges have a history. They 

 are widely diffused in our present seas. The chalk 

 formation of Europe abounds with them, and presents 

 forms even more varied and beautiful than those now 

 existing, but which must have lived at a time when 

 large parts of our present continents were in the 

 depths of the ocean. Still further back, in the 

 Silurian age, they seem to have been nearly equally 

 abundant. I have recently studied the microscopic 

 structures of a large collection from the Niagara 

 limestone, consisting of many species, each of which 

 presents arrangements of spicules as beautiful and 

 complex as those of the modern kinds. Still farther 



. N 



