98 • MULTIJM E PAEVO. 



a part more important than all the mighty monsters that 



Hved in ages past What purpose do these bodies 



serve ? It is highly possible that they form, in a great 

 measure, the food of all the minor aquatic animals more 

 highly organised than themselves ; I have often found, on 

 examining shrimps, that their stomachs, which are situated 

 behind the eyes, are entirely filled with diatoms. That 

 the siliceous shell passes through nearly intact, there can 

 be no doubt, but it is certain that the internal structure, 

 the endochrome, may be digested and form the nutritive 

 portion ; in this view I am borne out by referring to 

 guano — a most prolific source of fossil diatoms. Here 

 we find abundance of siliceous shells, in fact their presence 

 or absence is now the test of the genuineness of the 

 article ; — these, in past ages, must have been consumed 

 by small marine animals, these again consumed by fish, 

 and these in their turn by birds : in guano I have noticed 

 the proportion of diatoms to be in some specimens nearly 

 1 in 500 parts. A correspondent from Callao, writing to 

 the Illustrated London News, on the Cincha guano 

 islands, says the export of guano from the islands has 

 increased considerably during the last ten years ; between 

 800,000 tons and 400,000 tons are the annual amount at 

 present : here, in a very moderate calculation, from one 

 spot alone, we have the annual removal of 500 tons of 

 diatoms!' * 



The agency of these mighty but minute forms has been 

 still further developed in some researches of great interest 

 • Report of Cornwall Polyt. Soc. for 1857. 



