64 LIFE AND OKGAMSATION. 



Of the two great steps in knowledge here denoted, the 

 latter is doubtless the most remarkable, and replete with 

 problems of the deepest interest ; including time as one of 

 its foundations, and thereby bearing on the history and 

 destinies of Man himself. But the extraordinary multiplica- 

 tion of the number of recognised living species, though less 

 striking to the imagination, yet furnishes conclusions hardly 

 less important to the philosophy of life. It is difficult indeed 

 to define, even approximately, the amount of this multipli- 

 cation, which occurs chiefly, though by no means solely, in 

 the lower parts of the animal series. The powerful eye of 

 the microscope has shown, in earth, air, and water alike, new 

 forms of life, invisible to all unaided sense, but endless in 

 aspect and variety. Every bucket of water taken up from 

 mid-ocean teems with vitality. The dredgings of Forbes 

 and others ,in shallower seas show different zones of depth, 

 tenanted by different species of animal life. Even the bed 

 of the Atlantic, 10,000 or 12,000 feet below the surface, was 

 found, in soundings for the electric cable, to be covered with 

 the remains of Foraminifera which, for aught we can tell, 

 may have lived at this depth. We all know (and in hot 

 countries cogently feel) how thickly the air is peopled ; not 

 merely with the birds which crowd and ornament our 

 museums, but yet more with incalculable swarms of insect life, 

 even more audible than visible to sense. The tropical forest 

 is noisy day and night with the life it contains. The sea is 

 luminous with animal phosphorescence. Nearly two hundred 

 species of glow-worms, and forty or fifty of fire-flies, are cata- 

 logued as luminiferous animals of the land. The researches 

 of Ehrenberg, eminently successful among the fossil and 

 living Infusoria, have since been directed to the atmosphere ; 

 in which, by appropriate methods, his microscope has detected 

 numerous other minute species heretofore unseen and un- 

 known ; yet not indifferent, we may well believe, to those 



