SEA-FISHERIES LABORATORY. 3 ue) 
Even amongst the Diatoms, however, there are 
differences, Biddulphia, on account of its larger 
size and shape, being more abundant in the coarse 
net, and Chaetoceros and Coscinodiscus in the fine. 
This is wel] seen in the following examples of average 
catches prepared from ten pairs of figures, each pair 
consisting of fine and coarse net gatherings taken at the 
surface simultaneously during April. 
Fine Net Coarse Net 
(No. 20). (No. 6). 
ipiddulpliia ...... 38,769 sno | BroGOO) 
Chaetoceros ...... 406,355 ae 1,895 
Coscinodiscus ... 23,777 ae 5,000 
Copepoda ......... 156 ae 1,007 
Fish Eggs ..... meh 16 ae ql 
Dinoflagellata ..... 2,180 34 
The accompanying diagram (fig. 14) shows the 
eraphic relations of these two sets of figures, so as to 
illustrate the catching power of the two nets for the 
particular organisms. The columns are of necessity 
drawn to a different scale for each group, so that the 
lines for one group are not comparable with those for 
another—it is only the two catches of the same group that 
are comparable inter se. 
The conclusion at which we have arrived is that it is 
necessary to take both a coarse and a fine net gathering 
at the same time in order to get anything like an 
adequate sample of the plankton. It has been shown by 
several investigators that even the finest meshed silk fails 
to catch a considerable proportion of the minuter forms 
of the Protozoa and Protophyta. But it can also be 
shown that such fine nets do not succeed in bringing up 
a due proportion of the larger and more powerful 
swimming organisms, such as Crustacea—probably 
