692 
OCEANOGRAPHY: J. F. McCLENDON 
nearly normal as possible. Various substances were found to check 
entirely all muscular activity but leave cilia actively beating all over 
the 'body. The most satisfactory results were obtained after one and 
a half to two and a half hours treatment with a solution of magnesium 
chloride m/7 to m/9. When all trace of muscular contractility was 
lost, locomotion did not occur, even though the cilia were beating with 
far greater vigor than under normal conditions. A solution of lithium 
chloride m/45, applied for eighteen to twenty-two hours, checks entirely 
the beat of the cilila, and leaves the muscles sufhciently unaffected to 
permit of locomotion by gliding. In such tests entire freedom from 
mechanical vibrations is an absolute essential and care must be exer- 
cised in handling the treated specimens to avoid a strong mechanical 
stimulus. 
From these observations I conclude that the locomotion of planarians 
is essentially a muscular act in which the cilia play no necessary part. 
1 Contributions from the Zoological Laboratory of the Museum of Comparative Zoology 
at Harvard College. No. 301. 
DIURNAL CHANGES IN THE SEA AT TORTUGAS. FLORIDA 
By J. F. McClendon 
DEPARTMENT OF PHYSIOLOGY. UNIVERSITY OF MINNESOTA AND TORTUGAS LABORATORY. 
CARNEGIE INSTITUTION OF WASHINGTON 
Communicated by A. G. Mayer, September 21, 1917 
The only diurnal change noted in the Gulf Stream was a change in 
temperature of about 1° and the resulting change in oxygen tension. 
But in water shallow enough for considerable light to reach the bottom, 
marked diurnal changes were noted in temperature, hydrogen ion 
concentration (pH), total C02-concentration, CO2- tension, 02-concen- 
tration and 02-tension. The temperature, 02-concentration and O2- 
tension were lowest and the C02-concentration and C02-tension highest 
about 5 a.m. The temperature, 02-concentration and 02-tension were 
highest and C02-concentration and CO2- tension lowest at about 3 p.m., 
local apparent time during July. The magnitude and exact time of 
maxima and minima varied somewhat from day to day and varied a 
great deal with the location of the station at which the water was stud- 
ied. The diurnal curves showed secondary notches which were prob- 
ably due to tidal currents and eddies, since no such notches were pres- 
ent in the diurnal curves of stagnant sea water. The differences be- 
tween stations were evidently due to previous history of the water 
carried past the station by currents and to variations in depth and in 
