23 



London on the east coast round the south coast to Walfisli 

 Bay (or Swakopmund) on the west coast. 



It is of special interest also to note that, while at all other 

 places the occurrence seems to be more or less intermittent, 

 at Knysna and at Walfish Bay it is well recognised as an annual 

 one. At both of these places it occurs also at a definite time 

 of the year — the mid and late summer months. 



It is just on this coast that the cold Antarctic current going 

 from west to east strikes the continent of Africa, and meets 

 the warm Mozambique current coming southwards along the 

 east coast, and it may be supposed that Knysna is a point at 

 which forms of animal life, accustomed more or less to warmer 

 water than is found further west, would suffer more from the 

 inset of the cold water. (Compare the effects of cold on the 

 Frost-fish, p. 125.) 



The dying off of the fish at Wallish Bay seems more attribut- 

 able to the pollution of the water by decaying vegetable matter 

 accumulating in the bay from the sea. The dying off of the 

 diatoms may be due to the change of temperature which the 

 west coast division of the Antarctic current undergoes here, 

 just as the south coast division of the current does at Knysna 

 It may be of significance that Soles are frequently cast up at 

 Walfish Bay, but not at Knysna. They were notably absent 

 from the other occurrences. 



It is to be noted also that it is mainly the waters of the 

 immediate coast that are affected, pointing to an upswelling 

 of cold waters (Antarctic current V) from under the warmer 

 waters (Mozambique stream ?). 



These physical features are reflected in the forms of animal 

 life in the sea, the fauna of the east coast being markedly different 

 from that of the west. The Snoek, for instance, is a charac- 

 teristic west coast form, and occurs, at certain seasons, in 

 great abundance from Cape Point northwards. It is found 

 occasionally at Mossel Bay and Plettenberg Bay, but very 

 rarely at Port Elizabeth, and has not been recorded from the 

 east coast north of that town. It is a fish of the high seas and 

 only at times comes close inshore. It has never been men- 

 tioned as among the fish affected in the above cases, but it 

 may be accepted as established that its occurrence is largely 

 influenced directly or indirectly by the temperature of the 

 water. It is essentially a migratory fish, and doubtless its 

 abundance or scarcity on the coast of South Africa is dependent 

 to some extent at least on the temperature condition of the sea 

 at the season in which it approaches the shore. {Vide p. 116). 



The Red Stumpnose {Chrysophrys gihhiccps) may be taken 

 as a typical example of a warm-water fish. It extends from 

 the east coast along the south coast as far as False Bay. It is 

 [C.P. 6-'i4.] 



