256 DONALD J. MATTHEWS. 
maximum of 31 in August, followed by a fall to 17 in September. The 
curve shows that the maximum value for phosphates, 0-061 mg. of P.O; 
per litre, coincided with the smallest number of diatoms, and also with 
the shortest days of the year. The phosphates then commenced to fall 
at once, irregularly at first it is true, to a minimum, of less than one- 
tenth of the maximum, at the end of April, which coincides with the 
diatom maximum for the year. The number of diatoms fell off at the 
beginning of May, while the phosphate minimum continued to the last 
week of the month. At this period, however, the alga Phwocystis ap- 
peared in enormous quantities. It was first abundant on April 25, 
reached its maximum on May 9th and 12th, then declined, and was 
absent after June 12th. If the decrease in phosphates 1s to be attributed 
to their removal by alge, as the writer considers to be the case, some 
other factor must be sought in addition to the phytoplankton. This is 
probably to be found in the larger alge, such as Fucus, Laminaria and 
others. Well grown young plants of these are to be found in February, 
and must by that time have already abstracted considerable quantities 
of phosphorus from the water. The march of events would then be 
somewhat as follows. As soon as the young plants of the fixed alge 
begin to increase the amount of phosphates in the water falls off, and 
this decline is further hastened by the sudden increase of diatoms at 
the end of April. In May the diatoms decrease, but the phosphates are 
kept at a minimum value by the appearance of Phwocystis, and increase 
at once when this disappears in June. The want of data for phosphates 
in July and August prevents a further comparison with the figures for 
diatoms, but another minimum might be expected in August. Phosphate 
values are also missing in November and December, 1916, but the 
records for 1915 show an agreement with what might be expected from 
the diatom figures, that is, a rise from November to December. 
On January 10th, 1917, the amount of phosphates present was very 
nearly the mean of the first two figures for the month in the previous year. 
The Admiralty regulations have made it impossible to obtain water 
at a distance from the shore. It is by no means improbable that 
in mid-Channel, beyond the influence of the fixed weeds, the decrease 
in the phosphates would not be large until much later in the year when 
the phytoplankton begins to increase. 
The last column of the table contains some figures for the total dis- 
solved phosphorus, calculated to P,O;. It is not claimed that they are 
accurate, but they certainly show that what may be called for the 
present “ organic phosphorus ” is often high even when the phosphates 
are at a minimum, though it varies from month to month. The figures 
for June 27th, 1916, and January 10th, 1917, are probably the most 
