280, University of California Publications in Zoology \Vou-9 
has led me to believe that such a method is practically valueless. 
In this paper numbers of specimens taken with different nets 
are not adjusted to each other and allowance should be made 
for that fact. The effect of certain environmental conditions is 
plain even if we do not know, from the number of animals taken 
with a given net, the number that might have been expected 
under the same conditions but with another net. Accordingly, 
IT have followed the plan of considering the distribution of 
various species as shown by each of the four sorts of nets used, 
the catches with the different vertical closing nets being com- 
bined. 
Nineteen species have been chosen for a detailed study of 
distribution. The selection was based purely upon frequency 
of occurrence, for a form must be found reasonably often to 
make it profitable to study its distribution. It is believed that 
all of the species listed in table 11 were taken often enough to 
furnish a reliable basis for such a study. This table explains 
itself, but it should be noted that the lower numbers in each 
column and in lines 1-18 give the number of hauls in which 
the species was found. 
