106 MICROSCOPICAL OBJECTS FOUND 



rally upon the whole mass, can have produced 

 the change from a transparent and organized to 

 an opaque and inorganic condition, or all the 

 fragments of the minute Foraminifera would have 

 been more or less aifected in the same manner. 

 But such is not the case. The latter retain their 

 vitreous transparent aspect ; hence the amorphous 

 part of this deposit must either have been derived 

 from some other source than broken Foraminifera 

 and analogous minute structures, or it must have 

 been altered by some agency acting only upon some 

 of the atoms now constituting the stratified mass. 

 The digestive organs of molluscous, acephalous, 

 and other marine animals appear to be the only 

 instruments which would be likely to effect such 

 results. We have the copros of saurians and of 

 fish constituting extensive stratified layers, — why, 

 then, should we not have the excreta of molluscs 

 and other inferior animals ? Mr. Darwin met 

 with two species of fish in the neighbourhood of 

 Keeling Island belonging to the genus Sparus, 

 which feed entirely on coral. On opening their 

 intestines, he observed them to be distended with 

 yellowish calcareous matter ; and he adds : — 

 " These fish, together with the lithophagous 

 shells and Nereidous animals, which perforate 

 every block of dead coral, must be very efficient 



