1912] Esterly: Copepoda of the San Diego Region 279 
The list of species as they occurred in the open vertical hauls 
is given in table 10, which follows. 
No attempts have been made to standardise the catches of 
the different nets. It would be advisable to attempt this if we 
were studying the action of the types of nets used. But since 
we are primarily concerned with the biology of the copepods, and 
because certain facts are obtainable from our data without 
correlating, each sort of net is considered by itself. One cannot 
fail to notice that the catches of the horizontal and vertical 
closing nets do not always agree closely, particularly as to 
the location of the region of greatest abundance. Yet all the 
nets show a rather striking correspondence in regard to certain 
general features of the behavior of the Copepoda. 
It does not seem that standardisation of net catches with 
each other would really be of much value in view of the results 
of hauling with similar nets at the same time and almost in the 
same place. The idea that such standardising is valuable doubt- 
less grew out of the belief that plankton animals are uniformly 
distributed in the water. But such work as that of Herdman 
(1906), Herdman, Scott and Dakin (1909), or that of Michael 
(1911) has shown that distribution is irregular. Instances of 
this could be given almost without number in regard to the 
distribution of the copepods of this region. Standardisation 
would have to be based on factors that depend on the organisms 
themselves, that is on biological factors in cases where similar 
nets used at the same time and in as nearly the same manner as 
possible give very different results. It is likely, therefore, that 
attempting to adjust for different nets in regard to distance 
and rate of hauling, amount of water filtered, and lke factors 
is at least unnecessary when the nets are used at different times 
and under different conditions. We may reasonably expect 
that, if we deal with a large number of hauls well distributed 
over several months and through the twenty-four hours, we shall 
obtain results of worth in regard to the relation of the organisms 
to their environment. 
A possible method of standardising would be to allow for 
the difference in area of the mouths of nets. This was done in 
two earlier papers (Esterly, 191la, 1911b), but my experience 
