1912] Ritter: The Marine Biological Station of San Diego 173 
construction, or material is uncertain, but the tank leaked badly 
at first and no way was found of remedying the trouble except 
by resort to asphaltum for an inside dressing. This was appled 
by the membrane method, i.e., by alternating layers of asphaltum 
and burlap. Leakage was entirely stopped in this way. Whether 
sea-water in contact with these substances will become noxious 
to the sensitive organisms of the plankton remains to be deter- 
mined, but there are good grounds for hoping it will not. 
In the light of what we now know, apparently it would have 
been better had the building of the tank been deferred for a 
year or two. 
III. SCIENTIFIC EQUIPMENT OF THE LABORATORY, AND 
LABORATORY METHODS 
Mention has already been made of the fact that from the 
beginning the station has depended to a considerable extent on 
the department of zoology of the University of California for 
apparatus. This has been particularly true as regards micro- 
scopes. Gradually as finances have permitted, this dependence 
has been and is being overcome. Passing by the instruments, 
glassware, reagents and so on common to every biological labora- 
tory, reference need be made only to such things as are of 
interest because of the special work done and methods employed. 
On the biological side mention should be made of the im- 
portance of the Zeiss-Greenough binocular microscope in identi- 
fying, sorting and enumerating the vast numbers of organisms 
too small for the unaided eye or ordinary simple microscope, and 
too large for the compound microscope. Reference ought also to 
be made, though details are impossible, to the various devices 
employed in counting, measuring, and weighing organisms, and 
in recording data in the laboratory work. To a considerable 
extent these have been described in the several technical papers 
setting forth the researches in which they have been employed. 
They are spoken of here but without details to impress upon the 
reader the great but still subordinate importance of these aids 
to research. 
The equipment and methods used in the laboratory work on 
