1912] Ritter: The Marine Biological Station of San Diego 183 
An example may now be given of actual work in accordance 
with these general considerations, which has been for some time 
and is still being, carried on. 
On arriving at the station, which of course is ‘‘picked up’’ by 
sextant observation, a series of water samples and temperatures 
is first taken (see description of this operation, p. 189), this series 
corresponding in general with the depths at which the biological 
collections are to be made. In the programme here presented the 
depths are from 75-50, 50-40, 40-30, 30-25, 25-20, 20-15, 15-10, 
10-5, and 5-0 fathoms. The biological collections are made and 
immediately thereafter a second series of water samples and 
temperatures is taken similar to the first, and sextant observations 
taken to make sure of the position at the end of the operations. 
The ‘* Agassiz’’ then returns to the station and the observations 
are repeated. Three complete series on the same station can 
usually be secured between midnight and noon; one for darkness 
or very early morning twilight; one for twilight; and one for 
daylight. Although as previously stated seasonal distribution is 
made the central problem or point of departure in the pro- 
gramme, the operations yield in addition information as to the 
abundance and movements of organisms as affected by variations 
of (1) light, (2) temperature, (3) density of water, (4) topog- 
raphy of the sea bottom, and (5) the gaseous content of the 
water. One of the three stations having been thus worked, the 
next day another is occupied and the operations repeated as 
exactly as possible. The third day the remaining station is 
investigated. These three stations having been gone over, what 
shall be done next will depend on circumstances. Three more 
days may be spent on the same stations, taking them in the same 
or in a different order; stations in some other locality may be 
visited for the same kind of work; somewhat different work may 
be done; or the cruise may have been planned for going once 
over these three stations and no more. 
A copy of the log-book for one day, rearranged for con- 
venience of reading, will be instructive. The day, selected at 
random, is June 15, 1911. 
