MARINE BIOLOGICAL STATION AT PORT ERIN. 45 



distance of about 500 feet, parallel with the shore. The 

 contents of the net were emptied into a jar of sea-water, 

 containing in all 1,000 cnb. cm., which was thoroughly 

 stirred lip and then 1 cnb. cm. was taken ont with a 

 pipette from the centre of the jar as a fair representative 

 sample. This was spread ont in a large flat glass trough 

 under the microscope and the organisms were identified 

 and counted. The 1 cub. cm. which formed £-^^ part 

 of the whole gathering was found to contain 12 species of 

 larger planktonic organisms, such as Copepoda, larval 

 worms, Medusoids, &c, and of these larger forms there 

 were counted 150 individuals easily visible to the unaided 

 eye. If then the sample was a fair one, the jar probably 

 contained about 150,000 larger organisms visible to the 

 eye, and these were strained out of a column of water of, at 

 the utmost, 500 feet in length and 1 foot in diameter,* 

 which would amount to about 400 cubic feet. That would 

 give o75 of these organisms per cubic foot, or 60 per 

 gallon. If the other two hauls, which we had not leisure 

 on that occasion to treat in the same way, contained 

 organisms in the same proportion, then we had caught in 

 the space of about an hour something like 450,000 Cope- 

 poda and larvae, &c, visible to the eye, in addition to the 

 vast number of ])iatoms, Peridinians, and other micro- 

 scopic forms which were seen to be present in abundance. 

 I must repeat that these numbers are only given as a 

 rough approximation, and that they probably under- 

 estimate the number of organisms that were present. 

 Also it must be remembered that the waters of the bay 

 frequently contain far fewer organisms and sometimes 



* Probably a good deal less, because of the pressure on the net prevent- 

 ing the whole of the water from passing through. Consequently the 

 estimation is a minimum one, and more organisms are really present than 

 appears from the calculation. 



