i904-i9°5-] Recent Views regarding Coral Reefs. 175 



with some small powers of locomotion. But their dispersion 

 is accomplished chiefly by the action of surface currents, by 

 which they are drifted hither and thither far and wide. The 

 fry live mostly on minute vegetable organisms, which abound 

 in the plankton of which the fry form a part. While in the 

 immature stages they suffer a very high death-rate, which 

 arises from many causes. To begin with, they are an im- 

 portant source of food to many other animals. They are 

 liable to be drifted by surface currents to regions where the 

 water is not salt enough, or not sufficiently free from muddy 

 matter, or not warm enough, or not full enough of the food 

 they need. The chief risk arises from their liability to be 

 drifted into parts of the ocean where, at some time or other, 

 the temperature of the water falls below 68° Fahr. It has 

 to be remembered in this connection that, although the sun's 

 rays at the same time of the year heat alike all the ocean 

 water within the same latitudes, the final results are by no 

 means uniform. The action of the prevalent winds in some 

 cases, and of the Earth's easterly rotation in very many more, 

 seriously affect the surface temperatures. It must be remem- 

 bered that the great Antarctic basin is always chilling the 

 sea-waters there to icy coldness, and that these waters slowly 

 creep along the sea-bottom, flowing northward far beyond the 

 Equator. As they travel they tend to rise to the surface. 

 So nearly all the lower waters of the ocean have a tempera- 

 ture but little above the freezing-point, even where the 

 surface-waters may receive all day the burning rays of a 

 tropical sun. Now the Earth's rotation tends to bank up 

 the surface-waters on the east side of the great land masses, 

 and to make these surface-waters on the west side drift west- 

 ward from the land. This latter cause facilitates the slow 

 uprise of the nether waters. So there are cold Antarctic 

 currents rising on the south-west of Australia, on the south- 

 west of Africa, and on the south-west (or even all the west) 

 of the continent of America. Consequently there is not a 

 foot of the ocean surface on the west of either Africa or 

 America where, at some time of the year or other, the 

 temperature of the water does not fall below 68° Fahr. 

 There are therefore no coral reefs on the west coast of either 

 Africa or America. Nor are there any within several hundred 

 VOL. v. M 



