THE MICROPLANKTON OF PLYMOUTH SOUND. bi 
Chief forms—Gwinardia flaccida, Rhizosolenia species, Glenodinium 
bipes, Gymnodinium rhomboides, Pouchetia armata, Spirodinium spirale 
and glaucum, Phialidium hemisphericum, Obelia sp., Calanus finmarchicus, 
Temora longicornis, Acartia Claus, Portunus sp. zoea, Hippolyte and 
Porcellana larve. 
July. 
S. and 8.W. winds prevail. Fairly fine most of the month. 
Asterionella very common all the month. Chetoceras constrictum very 
common, C. curvisetum, very common at the end of the month only. 
Guinardia very common in the middle, not so common at the beginning 
and end of the month. Rhzzosolenia species very common, f. alata and 
R. Stolterfothii very common all the month, R. Shrubsole: not so common, 
R. setigera begins and gradually gets common, being very common at the 
end of the month. Peridimales not so numerous. Ceratiwm fusus very 
common in the middle of the month. Prorocentrum increasing. Infusoria 
fairly common, especially Tintinnopsis beroidea, which at times is exceed- 
ingly abundant. Phialidium and Obelia very common. Other medusie 
scarce. Calanus, Temora, Acartia and Pseudocalanus very common. 
Portunus sp. zoea and Porcellana zoea very common. Copepod nauplii 
common. Kchinopluteus common at the end of the month. 
Chief forms—Asterronella gaponica, Chetoceras constrictum, Rhizosolenra 
species, Ceratium fusus, Tintinnopsis berordea, Phialidium hemisphericum, 
Obelia sp., Pertunus and Porcellana zoex. 
August. 
Prevailing winds 8., some EH. and some W. Mostly fine weather. 
Second diatom maximum at the beginning of the month caused 
chiefly by Mastiglowa, Asterionella, Chetoceras, Lauderia, Rhizosolenra 
and Skeletonema which are all very common. Chetoceras constrictum the 
commonest. C. didymum very common on the 10th. Lithodesmium 
scarce at the beginning but very common at the end of the month. 
Rhizosolenra alata is very common until after the middle when it becomes 
scarce and very rare at the end of the month. AR. hebetata {. semaspina 
very common at the beginning, disappears at the end, R. setigera very 
common after the middle but scarce at the end, R. Stolterfothzi very common 
for the whole month. Skeletonema very common for most of the month, 
Peridiniales fairly frequent, especially Prorocentrum micans. Infusoria 
fairly abundant, especially Tintinnus subulatus and Tintinnopsis beroidea. 
Dictyocha and Distephanus begin in the middle of the month, Phialidium 
and Obelia very common. Muggicea atlantica becomes common at the 
end of the month. Copepods abundant. Calanus, Centropages typicus 
