| 54 THE MARINE AQUARIUM. 
a clear view of the bottom, and a vase does not admit of 
| this unless we look from above, the amount of refraction 
being very great at the base of the vessel. Hence, 
though marine stock may be well kept in vases, it must 
| 
be borne in mind that such vessels are far inferior as to 
the means of inspection to rectangular tanks. 
It is also important to bear in mind that marine stock | 
invites the use of the microscope in a greater degree than 
| Tiver specimens, and a flat-sided vessel is the only one 
a ee 
which affords proper facilities for the application of a 
magnifier to its contents. 3 
Stained Glass.—But there is a still more important 
matter requiring notice here. We are indebted to that 
accurate observer, Mr. Warington, for valuable informa- 
tion on the effects of light upon certain forms of sea 
weeds, and his mode of overcoming this is by passing 
light through variously coloured media. It can easily be 
understood, that plants, whose natural habitat is at a con- 
siderable depth beneath the surface of the ocean, bear ex- 
posure to the full daylight very indifferently, and that 
some special arrangements are necessary in order to cause 
the solar rays to fall upon them as nearly as possible in 
the same manner as in the twilight recesses from which 
they have been removed. ‘This is accomplished by fitting 
that side of the tank, which is intended to be placed next 
the window, with a sheet of glass stained of a soft sea 
green, and the softened light, so admitted to the tanks, 
promotes the healthy growth of the Alge, and very 
materially increases the beauty of the vessel as seen from 
the other side. Mr. Lloyd, whose ripe experience ever — 
| 
