THE MICROPLANKTON OF PLYMOUTH SOUND. 17d) 
Biddulphia mobihensis not so common, regia rare, sinensis more 
common, Lauderia common, Nitzschia delicatissima common at the end, 
Skeletonema very common, Streptotheca verv common at the beginning, 
rare at the end, Thalassiosira gravida common. Ceratiwm fusus, Per- 
dinium spp. and Prorocentrum not very common but occur throughout 
the month. Pheocystis very common at the end. Phialidiwm and 
Obelia become common at the end of the month, Steenstrupia rubra and 
Clytia volubilis occur rarely, Rathkea octopunctata very common, 
Arachnactis, Muggiwa and Hybocodon occur through the month but not 
commonly except Hybocodon at the end of the month. Terebellid larvee 
fairly common, Sagitta rare. 
Calanus very common at the end of the month, Temora and Pseudo- 
calanus very common. Portwnus sp. zoea very common, copepod nauplius 
and Balanus nauplius very common. Cypris stage of Balanus begins at the 
end of the month. Young fish and fish eggs rare. 
Chief forms—Chetoceras curvisetum, Lauderia borealis, Skeletonema 
constatum, Thalassiosira gravida, Rathkea octopunctata, Temora longi- 
cornis, Pseudocalanus elongatus, Portunus sp. zoea, Balanus and copepod 
nauplil. 
May. 
Prevailing winds 8. and 8.W. Sometimes E. and N.W. Weather 
variable, fine at the end with S. and 8.W. winds. 
Chetoceras species common, especially C. curvisetum and pseudo- 
cruutum, Lauderia very common at the beginning, dwindles at the end 
of the month. Mastigloia sp. in large numbers from the middle to the 
end of the month, Nitzschia delicatissima very common, Rhizosolenra 
species increasing, Rk. Shrubsoler very common, &. Stolterfothi gradually 
increasing so that it is very common at the end of the month, &. hebetata 
and semispina very common from the middle to the end of the month, 
R. alata occurs through the whole month but is not common. Skele- 
tonema very common. Thalassiosira gravida common. Various 
Peridiniales occur but not in large numbers. Infusoria too in small 
numbers abound. Phwocystis Pouchetii is very common through the 
whole month. Ameoebe fairly common. Phialidiwm and Obelia are very 
common and various other meduse are present. Sagita is not common 
and disappears at the end of the month. Calanus, Temora, Acartia and 
Pseudocalanus are abundant, Paracalanus very common early in the 
month, several other copepods present in smaller numbers. Portwnus sp. 
zoea is common, Megalopa stages appear in the middle of the month. 
Various other Crustacea larve are present, of these Hapagurus, Porcellana 
and Corystes are common. Evadne Nordmanni and Podon intermedius 
