THE MICROPLANKTON OF PLYMOUTH SOUND. 137 
Fig. 1 having a large spring and a small summer maximum (Lohmann, 
1908, table XIT). 
Of his numerical results the Peridiniales are relatively in much larger 
numbers than in the present records. Although here many species are 
found to occur and several new species are described, the individual 
numbers are usually enormously less in these records, even when the 
2000.—_____—__——___--_— 
1500} aan = == 
SKELETONEMA COSTATUM 
1000 lh = = - = | Pee neet! 
21010) ape Sea 
£00 > eee eee em ra oan 
WOO Fal = a ee ee || ee eee Sas a 
200 Sues Sea cabelas ae aaa 
——=¢ v e A 
SEPi., OCI. NOV. DEC. NAN. FEB. MAR. APR. MAY JUNE JULY AUG, SEPT. 
1915 1916 
Fic. 1.—Curve of Skelctonema costatum, showing average number of individuals 
in 50 ec. for each month. 
season of maximum number agrees. As Lohmann observed at Kiel, so 
here, there are several amcebe to be found in the plankton. Ours are of 
three kinds, one of which is fairly common. With him Flagellata are 
much more numerous than with us, except Pheocystis, which is so abundant 
here in May and June that it interferes with everything, clogging up all 
the nets. Infusoria Lohmann finds numerous, and there are numerous 
species of them here, but they are not found in large numbers with the 
exception of the Tintinnoidea. The smaller forms, such as Laboea species 
