88 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
The horizontal distribution of the plankton is con- 
sequently lable to be very variable and irregular, and 
although its characteristic constitution at different times 
of the year may be described, and the relative abundance 
of the different groups discussed, it is very doubtful 
whether any numerical estimates can be framed which 
will be applicable to wide areas. 
Tt is clear that samples taken quarterly, monthly, or 
even fortnightly, are quite inadequate to convey a correct 
idea of the constitution and changes of the plankton of a 
sea-area in any detail; and, consequently, conclusions 
ought not to be drawn from such insufficient observations. 
Samples, taken weekly throughout the year, and almost 
daily during the three most critical months, give by no 
means too much information, but will probably suffice to 
enable one to make that detailed comparison between 
adjacent localities and dates which are necessary for the 
purpose of determining the representative value of such 
periodic samples. 
L.M.B.C. Memorrs. 
Dr. Pearson’s important Memoir on Cancer, the 
edible crab, was published last summer, and is one of 
the largest and most comprehensive monographs of this 
series, extending as it does to over 200 pages and 12 plates. 
The next Memoir, No. XVII., on Prcren, the scallop, by 
Mr. Dakin is now in type, and will be issued 
immediately after this report before the end of the 
year. The following Memoir, No. XVIII, on 
ELeponr, by Miss A. Isgrove, is completed, and the 
MS. and drawings are now in my hands awaiting 
publication. Doris, the sea-lemon, by Sir Charles Eliot, 
and other Memoirs are also far advanced; and we hope to 
have a Memoir on our Irish Sea species of Ceratium and 
