116 THE MICEOSCOPIST IN BERMUDA. 



and its abundance of marine invertebrate life. I went there 

 with my little pocket microscope, to examine among the curious 

 and interesting things of the ocean shore. It was almost my 

 first lesson in microscopy, at least in the preparation of micro- 

 scopic objects; and my story I hope will be an incentive to you 

 to study nature and to gain knowledge, wherever you may 

 chance to ramble or journey. 



The Bermudas, in latitude 32 15', are the most northerly lands 

 where the reef-building corals grow. These little tropical ani- 

 mals can flourish only in water which never falls below the 

 temperature of 68; and the clearer and salter that water is the 

 better it suits them. In these respects the Bermuda Islands are 

 admirably adapted to them. For while it never freezes there, 

 there are also no fresh water streams to either muddy the ocean 

 water or diminish its saltiness. These animals, belonging to the 

 lowest order of beings that are provided with stomachs the so 

 called Gastrula type have the power of secreting large quan- 

 tities of carbonate of lime from the sea-water. And although so 

 small individually as to be scarcely distinguishable by the naked 

 eye, yet by the enormous increase of their numbers by budding, 

 they are able to build up barriers that inclose continents and 

 make islands. The branching species may grow to the height of 

 six or eight feet ; and the brain corals may make solid hemi- 

 spheres 15 or 20 feet in diameter. These extreme sizes however 

 are only found in more tropical waters. I have never seen them 

 in Bermuda even the half of these dimensions. 



The reef corals do not grow on bottoms deeper than one hun- 

 dred feet, and never quite up to the lowest tide level. So that 

 they are really confined to narrow vertical limits, and would 

 never produce appreciable effects if it were not for the fact that 

 nearly all shores are, in the long course of geological ages, grad- 

 ually either sinking or rising. It is a mistake to suppose that 

 the reef-building corals construct, directly from their growth, a 

 solid wall of coral material. They only rear a forest of branch- 

 ing stems, into which the waves w T ash up shells and bones and 

 broken fragments, which are all cemented into a solid mass by 

 the deposition of carbonate of lime from the sea-water. And on 



