178 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
OcEANIC AND NERITIC PLANKTON. 
Let us examine now the evidence that our observa- 
tions afford as to the so-called oceanic or neritic nature 
of the plankton in the several localities, and the bearing, 
if any, of such conclusions as to the origin of the 
organisms upon the hydrography of the area under 
consideration. 
It is not clear that all recent writers have used the 
terms ‘‘oceanic’’ and ‘‘neritic’’ in quite the same 
sense, so it 1s necessary to state exactly the meanings 
which we shall attach to the words. Our definition, 
which agrees in essentials with MHaeckel’s original 
statement (“‘ Plankton-Studien, 1890’’) would be as 
follows :— 
‘“Oceanic’’ species are such as are characteristic 
of the open sea, although they may occasionally or 
periodically be carried inshore and become mixed in 
varying proportion with the coastal plankton. They 
have no fixed. or resting bottom-stages in their life- 
history, and are therefore holoplanktonic. 
‘‘ Neritic ’’ species have their origin and their home 
in coastal waters, and although they may spread to some 
extent out to sea, they cannot live and reproduce there 
indefinitely, and consequently are not found normally in 
the open ocean. Many of them have fixed or resting 
bottom-stages in their life-history, and so belong to the 
meroplankton ; but some neritic forms are holoplanktonic, 
being permanently free. 
It is evident, then, that particular samples of 
plankton may be some of them oceanic and some neritic, 
while others will contain both oceanic and_ neritic 
species; but unless a considerable proportion of species 
from another source is present, conclusions ought not to 
