140 MARIE V. LEBOUR. 
flagellata Dictyocha fibula and Distephanus speculum are few in numbers 
as in our records, also the individual numbers of the Peridiniales which 
are often represented by single examples or by twos and threes. It is, 
however, among the Infusoria that a great difference is seen, for whereas 
my own records seldom show more than a few specimens in each sample, 
the small Infusoria are in fairly large numbers in the Dutch records, 
especially the species of Laboea, which sometimes reach five figures per 
litre. The Metazoa agree with my records in only being represented by 
very few individuals. 
Herdman’s (1908-15) quantitative estimates of the plankton for 
Port Erin and the south end of the Isle of Man are taken from the tow 
nets only. These are only comparable with the present records to a certain 
degree, but some facts stand out as of special interest. Here we find the 
large spring and smaller autumn maximum for the diatoms, the seasonal 
distribution of certain genera and their maxima, Rhizosolenia species 
in June; Chetoceras, Thalassiosira and Lauderia in April and May ; 
Chetoceras and Lauderia again in September and October; all these 
agree well with our records. The species of Beddulphia agree in being 
almost entirely absent from June to August and being much the most 
common from November to May. Coscinodiscus again agrees in being 
absent in the summer and early autumn and common in winter and early 
spring, Rhizosolenia species being only common in summer. Thalas- 
svosira has its maximum in May both at Port Erin and Plymouth, with a 
shght second maximum at Plymouth in 1916. Gwinardia is slightly 
earlier at Port Erin than at Plymouth. Lauderia with a large spring 
and small autumn maximum at both places, and the same with Chetoceras. 
Asterionella japonica appeared in large quantities in May, 1913, at Port 
Erin. At Plymouth it has a maximum in July and is present on and off 
from April to January, common through July and August. Apparently 
this species is irregular in its appearances, as Gough records it from 
Plymouth as ec in May. The numbers of Peridiniales at Port Erin are 
enormous compared with the present results ; Ceratiwm species and the 
larger Peridinium species forming the basis of the Port Erin records. 
However, we are in agreement in finding the Peridiniales maximum to 
occur very shortly after the diatom maximum and the maximum a single 
one which is only in the summer, May usually at Port Erin, June this 
year for Plymouth, when the curve shows a conspicuous hump, gradually 
dwindling in September, after which month very few are present. The 
smaller Peridiniales are not taken into account in the Port Erin reports, 
and the Gymnodiniacee, which turn out to be abundant, are necessarily 
not noticed as they come through the nets. The same applies to the 
other small unicellular organisms. 
