SEA-FISHERIES LABORATORY. 179 
be drawn as to the mixing of waters of diverse origin— 
far-reaching hydrographic conclusions ought not to be 
based upon the presence of a few individuals of supposed 
oceanic species in a neritic gathering. 
It is difficult, in the first place, to feel certain as to 
which are oceanic and which are neritic species. Previous 
writers who have published lists, such as Cleve, Gough 
and Gran, are not always in agreement, and even when 
they are it seems in some cases an agreement due to 
there being few recorded occurrences rather than to a 
full knowledge of the distribution of the species. There 
is some danger of deceptive reasoning if species are 
classed, say, as oceanic on a comparatively small number 
of records, and if thereafter the occurrence of such 
species in any localities is used as an indication of the 
oceanic origin of the water. It is improbable that all 
planktonic species are either oceanic or neritic. It may 
well be that some species are intermediate in character 
and habitat, overlapping and intermingling with both, 
and lable to be placed sometimes in the one category 
and sometimes in the other. Then again, there may be 
some species which are cosmopolitan, or ‘‘ Panthalassic,”’ 
as we should prefer to call it, occurring both in the open 
oceans and also in the shallower coastal waters of some 
parts of the world. 
The suggestion has been made* that amongst 
Diatoms the power of forming ‘“‘ resting-spores ’”’ 
(‘* Dauersporen’’ or ‘* Dauerzellen’’) might properly 
be regarded as diagnostic of neritic species; but although 
it is natural to suppose that neritic species would be the 
first to develop such a dormant phase, it must not be 
assumed without proof that resting-spore formation 
cannot take place in any oceanic species, and therefore 
* Hjort and Gran, Norwegian Marine Investigations, 1895-97, 
Bergens Museum, 1899. 
