THE MICROSCOPE IN GEOLOGY. 113 



embedded in a granular matrix."* These calcareous 

 shells, which belong to the Foraminiferous group, con- 

 tain living inhabitants ; at least, those which lie on the 

 surface layer of the ooze do, whilst deeper layers are 

 chiefly made up of the empty shells of Globigerinae. 

 The animal is "a mere particle of living jelly, without 

 defined parts of any kind, without a mouth, nerves, 

 muscles, or distinct organs, and only manifesting its 

 vitality to ordinary observation by thrusting out and 

 retracting, from all parts of its surface, long filamentous 

 processes which serve for arms and legs. Yet this 

 amorphous particle, devoid of everything which in the 

 higher animals we call organs, is capable of feeding, 

 growing, and multiplying ; of separating from the ocean 

 the small proportion of carbonate of lime which is 

 dissolved in sea-water ; and of building up that sub- 

 stance into a skeleton for itself, according to a pattern 

 which can be imitated by no other known agency." 

 And here I must guard you against Dr. Carpenter's 

 opinion, that the deposit of Globigerina-mud " has 

 been going on over some part or other of the North 

 Atlantic sea-bed from the Cretaceous epoch to the pre- 

 sent time as there is much reason to think that it did 

 elsewhere in anterior geological periods this mud 

 being not merely a chalk formation, but a continuation 

 of the chalk formation, so that we may be said to be 

 still living in the Cretaceous period" an idea which, 

 to use Sir Charles Lyell's words, is as inadmissible in a 

 geographical as a geological sense. You are doubt- 

 less familiar with those flinty nodules so extremely 

 abundant in the chalk formation ; you are certainly 

 familiar with that common, but very interesting article, 

 a sponge. What connection has the framework of the 

 softest of animals with one of the hardest of stones ? 

 The microscope reveals the fact that flint contains 



* Huxley's " Lay Sermons," &c. " On a Piece of Chalk." 



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