NAVICULA VENETA. 43 
Navicula veneta, Kiitzing. 
Navicula veneta, Kiitz. Bac. p. 96, t. xxx. fig. 76; Rabenh. Siissw. Diat. 
p- 39, t. vi. fig. 83; Ralfs, in Prit. Inf, p. 901. 
Navicula gregaria, Donkin, Quart. Micr. Journ. n. s. vol. i. p. 10, pl. i. 
fig. 10; Rabenh. Europ. Diat. p. 177. 
Navicula eryptocephala, var., Rabenh, Europ. Diat. p. 198. 
Plate VI. fig. 13. 
Frustule minute. V. broadly lanceolate, with slightly pro- 
duced subacute apices; strie rather indistinct, fine, 
connivent, reaching to the median line. 
This, though minute, is an exceedingly interesting 
species, in consequence of having the power of locomotion 
very highly developed. After having been well shook in a 
bottle and then placed under the microscope, it displays at 
first great uneasiness and activity ; several individuals may 
be seen directing their course simultaneously, and as it 
were voluntarily, towards any extraneous object near them ; 
to this they soon attach themselves in groups and adhere 
with wonderful tenacity, remaining at rest when they have 
once fixed themselves. This highly interesting pheno- 
menon can be readily observed, as this species is very 
abundant, and may be collected in large quantities. 
Hab. Submarine. It is abundant in estuaries and har- 
bours between tide-marks, especially where small streams 
pass over the sandy beach into the sea. In such situations 
it is therefore covered with fresh water for a short period 
during ebb tide and with salt-water for several hours during 
the flow. It is not, however, confined to the beach, but 
frequently forms an olive stratum ou the surface of piers, 
stones, and piles in our harbours. 
