1918] Essenhcvg: Distribution of the Polynoidae 209 



of water oceanic life may be carried away. This action is especially 

 noticeable after severe storms when deep water animals are found 

 washed ashore and when marine algae whose habitat is far off the 

 shores are also abundant on the beach. The same phenomenon is 

 known to occur on other coasts. After a severe storm the beach of 

 St. Andrews, Scotland, is known to be strewn with multitudes of 

 Aphrodita aculeata. These aphrodites are driven by the currents from 

 the offshore grounds, where they normally live in deep waters. 



Many times after the retiring tides, the beach for a distance of a 

 mile or more has been covered with aphrodites and other deep water 

 species (Mcintosh, 1900). Gattyana cirrosa, M^hich normally occupies 

 a depth of 600 fathoms in that region, has been found on the beach 

 after storms. Similar observations on the effect of storms have been 

 made on the coasts of Scandinavia. Since deep water species are 

 driven to the shores it is also probable that severe storms or even the 

 prevailing winds with their constant action on the waters may drive 

 animals from the shores into the depths. 



V. Chemical Composition of Water 



As another factor controlling distribution may be mentioned the 

 chemical composition of the water. The differences in salinity may 

 influence the distribution of Polynoidae to some extent. Some species 

 of Polynoidae can live in brackish waters as well as in salt. Some 

 species have even been found in river estuaries. Others, again, are 

 restricted to salt waters only. It is found that species most widely 

 distributed live under more varied conditions, while very restricted 

 species usually occur in similar environment even when they are found 

 widely separated. Evidently some species have acquired a greater 

 plasticity, while others may be more sensitive to changes in tempera- 

 ture and to chemical effects, and would either perish or undergo con- 

 siderable changes. These chemical differences may also explain the 

 greater number of genera and species in the great depths, if their 

 environment were altered. Most probably littoral polynoids, migrat- 

 ing or driven to the depths of the ocean, are in a more or less patho- 

 logical condition in the abnormal environment, and undergo such 

 radical changes that they soon lose their identity with the ancestral 

 shore species. That animals in great depths undergo pathological 

 changes has been revealed by the studies on crinoids (Clark, 1915). 

 These animals reach their minimum specialization between 550 and 



