GEOLOGICAL. 183 



millions of such once-living bodies have been reckoned. 

 How hard such stone becomes, and how durable, you may 

 believe when I tell you that the paving- stones of the 

 London Koyal Exchange, where " merchants most do 

 congregate," and which were laid there when the first 

 building was erected in the reign of Queen Elizabeth 

 that is, three hundred years ago, are there still, though 

 trodden by the millions of feet of men who have long 

 since gone to their account. 



Now, while I show you some of the best specimens I 

 have seen of these Foraminifera in their natural, that 

 is their now fossiliferous form, let me tell you how they 

 came into my possession. 



My good friend, Mr. E. H. Robertson, to whom I am. 

 indebted for many interesting facts connected with this 

 subject, begged me to get him a quantity of that tine 

 sand which the importers of sponge beat out of the speci- 

 mens before they are offered for sale. 



When the sponge of commerce, which is really the 

 skeleton of an animal from which the fleshy part has 

 passed away, was living, it was of a soft gelatinous nature. 

 The openings which you see in an ordinary mass, such as 

 that used for washing purposes, are the mouths, if we 

 may so call them, of the living sponge, through which 

 the life-giving air passes into the animal, and through 

 vhich is carried the small portions of animal matter on 

 which sponges feed. 



Now, these little Foraminifera (so called from the two 

 Latin words -foramen, an opening, and fero, I bear) 

 evidently were to the living sponge just what swallowing 

 power is to a living man ; and everybody knows what 

 the result would be were he to attempt to swallow 

 an oystor, shell and all. That is precisely the result in 

 the case of the sponge. The minute shells of the Fora- 



