Notes . 
579 
way large numbers of Diatoms are to be found in the mud of the 
river’s bed. These were described as far back as 1854 by Roper 1 , 
who having examined the mud from Hammersmith and from spots 
lower down the river remarks on the large number of marine species 
present. Even at Kew a few truly marine species (e. g. Coscinodiscus 
radia/us, Surirella ova/a, Rhaphoneis Rhombus ) were found, and had 
my observations extended over a greater length of time more would 
probably have been discovered. I do not think that many of the 
freshwater forms found in the upper reaches of the river will be met 
with much further down than Kew, although Hensen 2 and Brandt 3 
found a number of freshwater Plankton-species, present in some cases 
in quite considerable quantity, in the slightly brackish water of the 
Stettiner Haff. 
My collecting was performed between Kew and Cookham on six 
separate days during a period of a little more than a month. The 
dates, together with the temperature of the water and the nature of the 
weather, may be mentioned at once so as to save repetition : — 
(1) Kew-Richmond : August 14; i8°C; bright, with a few clouds 
at intervals. 
(2) Richmond-Teddington : July 11 ; 20° C ; slightly cloudy. 
(3) Hampton Court-Sunbury : July 16 ; 23 0 C ; overcast. 
(4) Shepperton-Weybridge : July 26 ; i8-J°C; cloudy, water very 
much disturbed. 
(5) Datchet- Windsor : August 8 ; i 84 °C; rainy. 
(6) Maidenhead-Cookham ; August 19; i8°C; bright, with a few 
clouds at intervals. 
All the samples were collected from a rowing-boat with the help of 
an ordinary funnel-shaped net of fine gauze, the lower narrow end 
being attached to a glass tube. Samples were collected from the 
surface of the water, and in some cases from deeper strata, the net 
being maintained below the surface at a depth of 1-2 feet. The net 
was usually allowed to remain in the water for a period of about three 
minutes, during which the boat was rowed at a medium rate. The 
samples were examined the same day or the day after they were 
1 On the Diatomaceae of the Thames. Trans. Microscop. Soc. of London. 
New Series, vol. ii, 1854. 
2 Das Plankton der ostlichen Ostsee und des Stettiner Haffs. Sechster Ber. der 
Commission zur wissenschaftl. Unters. dentscher Meere, 1890. 
8 Ueber das Stettiner Haff. Same periodical, vol. ii, 1895 (new series). 
