6 BULLETIN OF THE NATURAL HISTORY SOCIETY. 



Modern Faunas of the oceanic tracts. 



Among these lowly forms are the Foramenifera, the great 

 majority of which are rery small, and many so minute that 

 they cannot be seen without a microscope. Animals of this 

 kind constitute the bulk of the English chalk, and are now 

 being showered down in countless numbers on the bottom 

 of the sea, in its warmer parts. The mud which covers the 

 submarine plateau in the North Atlantic, where the electric 

 cables are laid, is largely composed of the shells of Foramen- 

 ifera, some large enough to be seen with the naked eye, 

 others invisible. 



Another class of these low organisms of the ocean is that 

 typified by the Sertularian Zoophites. These little creatures 

 live in colonies attached to the *' gulf-weed" which floats on 

 the surface of the Atlantic. The gulf-weed is a kind of sea- 

 weed (Sargassum nutans) which floats on the broad surface 

 of the Atlantic, south of the Gulf Stream ; it is so abundant 

 in some areas as to conceal the surface of the sea itself. 

 These tracts of the ocean, undulating with every billow, have 

 been compared to vast pasture fields. Such a tract is the 

 Sargasso Sea : uch another is found in the Pacific Ocean. 

 The imagination would lead one to think that these weeds 

 must seriously impede navigation ; and it was in this sea that 

 the sailors of Columbus became so much alarmed, that their 

 commander had great difficulty in persuading them to con- 

 tinue their voyage. 



The gulf- weed harbors a minute world of its own; here we 

 find little crabs crawling about, and other minute crustaceans 

 take shelter under its branches. Small fish may be seen to 

 harbour in the weeds, sheltered there from their enemies, as 

 they would be in the weeds that still grow along the shores of 

 the sea, or in the rivers. 



Another class of little creatures which are found in the 

 open ocean are the Pteropods, or, as the French call them, 

 " Butterflies of the Sea." They are so called because their 

 organs of locomotion consist of two little tins, or membrana- 



