36 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
maximum; but in bulk, even at the maximum, the 
Zoo-plankton, except on rare occasions, is small compared 
with the spring gatherings of Phyto-plankton. A 
Phyto-plankton gathering in the Irish Sea is practically 
only obtainable in spring or in late autumn; and if the 
gathering be a very large one, it is certain to have been 
taken at the former period, say between the middle of 
March and the middle of May. 

Fic. 10.—A Phyto-plankton gathering Fic. 11.—A Zoo-plankton gathering 
consisting mainly of Diatoms consisting mainly of Copepoda 
(Thalassiosira). (Acartia). 
[From photo-micrographs by Edwin 
Thompson. ] 
But in the Hebrides, as we have seen, very large Phyto- 
plankton hauls (fig. 10) may be taken year after yearin July— 
when in the Irish Sea the hauls are for the most part com- 
paratively small, and are all composed of Zoo-plankton 
(fig. 11). Mr. Andrew Scott, A.L.S., who has been 
