or 
md 
conditions on the beds, and it becomes necessary to fall 
back upon other methods which may not give altogether 
conclusive results from a critically scientific point of view. 
To remove animals from their natural surroundings and 
place them in confinement in a limited area of water is 
undoubtedly detrimental to life processes at first. After 
some time the effects produced by the change may how- 
ever be diminished, and the animals become acclimatised 
and live probably very much as they would have done had 
they been left in their original state. We are thus 
enabled to carry on observations which would be quite 
impossible under natural conditions. 
Large samples, about + ewt., of mussels were collected 
from the Roosebeck outer scar and from a scar in Barrow 
Channel which only ebbs dry at low water of spring tides. 
These were placed in the tanks in September, 1899, and 
kept under observation for twelve months. <A constant 
current of sea water was maintained, and from time to 
time, usually twice a week, small quantities of mud, known 
to contain diatoms, &c., were added to supply the animals 
with food. The animals were examined microscopically 
at intervals, and the reproductive organs compared with 
samples taken direct from the beds.. The rate of develop- 
ment was found to be practically the same in the mussels 
in the tanks and in those on the beds. 
On May 6th the mussels from both beds commenced to 
discharge eggs. These were isolated and examined under 
the microscope. No development took place. No ripe 
males were found at this period, and it may be concluded 
that these eggs were not fertilised. The mussels con- 
tinued to discharge eggs which underwent no change until 
June 14th. On June 13th the first obvious discharge of 
spermatozoa occurred. This was from the mussels from 
Barrow Channel, and so abundant was the supply that 
