4 :\ll'sK^^r. hk'ookia'x institutk of arts axd sciknoes. 



and their local fauna is not roinforccd by creatures -cliaractei-istic of the 

 current. It is interesting- to observe, however, that at the Tortuj;as we find 

 more than a mere concentration of individuals, for a number of characteris- 

 tic species aj>])ear to be confined to this region alone. 



Moreover, at the Tortugas we have a small land mass surrounded by 

 pure, deep ocean water, while at the Bahamas we find vast areas of shallow 

 Hats, covered mainly with coralline mud. These great banks of the Bahamas 

 are veritable submarine deserts, covered only with a sparse growth of coral- 

 line, alg;e, and with here and there a cluster of reef-corals and gorgonians. 



It is remarkable, also, that the water over these shallow banks is almost 

 as deficient in life as is the desert bottom itself. Almost no Sagittie, Salpaj 

 or Crustacea being found, and among Medusje only Olindias, Cubaia, and 

 Lymnorea are abundant. 



Indeed, the water over the banks is usually charged with a flocculent 

 mass of silt, which readily adheres to pelagic animals, and apjjears to be ra- 

 pidly fatal to them. Only in this manner can we account for the poverty of 

 pelagic life over the Bahama banks, for the deep-water regions of the Baha- 

 mas, such as the Tongue of the Ocean or the area to the eastward of Great 

 Abaco Island, are rich in pelagic animals, which appear to be free from silt 

 and in excellent condition. The water fi-om the deep areas must, however, 

 often be driven over the shallow banks and its life destroyed. 



The coral reefs of the Bahamas are richer in species than are those of 

 the Tortugas. The\' are best developed along the windward edges of the 

 banks, the richest single reef being probably that which extends along almost 

 the entire eastern shore of the Andros Islands, about one mile out from the 

 beach. On the other hand fewer species of marine invertebrates and fishes 

 are found among the Bahama reefs than among those of the Tortugas. The 

 actual area occupied by corals is insignificant in comparison with the great 

 extent of barren flats around them. 



In general it appears that while the Tortugas fauna is recruited from the 

 pelagic life of the (Jnlf Stream, and from the drift caused by prevailing 

 winds, the Bahama fauna is depleted by the same winds, and is poor in those 

 creatures which are mainly dependent upon great currents for their distri- 

 bution. 



Morj)]iolof/!/, etc. A unique opportunity was afforded for the study of the 

 post-embryonic development of Cubaia, and Olindias, and it appears that 



