82 MR. F. BALFOUR BROWNE ON AQUATIC COLEOPTERA. 
From the table it will be seen that the same species are not 
as a rule dominant in each list. 27 species show a plus value 
with H. pictus, 34 with H. granulans, and igwith II. gyllenhalii. 
Sixteen out of the 27 species in the “ Pictus ” column appear 
in the “ Granularis ” column, while only three are common 
to the “ Pictus ” and “Gyllenhalii” lists. On the other hand, 
16 species are common to “ Granularis ” and “ Gyllenhalii.” 
This suggests that the group of species usually associated with 
H. granularis may occur mixed with the group usually 
associated with H. pictus and also that the “ granularis ” and 
“ gyllenhalii ” groups may occur mixed. The “ Pictus ” and 
“ Gyllenhalii ” groups are however quite distinct, presumably 
indicating a different normal habitat of the species of the two 
groups. That the “ granularis ” group should occur mixed 
with both the other groups suggests that it is capable of 
division into two groups, one towards “pictus” the other 
towards “ gyllenhalii,” or perhaps that the “ granularis ” 
group has a wider range than either of the others. However, 
as I have said, my object in referring to this part of the subject 
was to acquaint you with the method, and that I have en- 
deavoured to do. No doubt further observations will modify 
some of the figures attached to the species in the above table, 
as some, such as Ccelambus versicolor and Cnemidotus impressus 
have not occurred in sufficient collections to make their 
exalted positions assured. No doubt when more of the groups 
are worked out cross references such as “ A ” in “ B ” collec- 
tions and “ B ” in “ A ” collections will also modify some of 
the values, but on the whole I believe the method is sound 
and will yield positive results. 
I have now endeavoured to give you a resume of the main 
facts which have appeared in the course of systematically 
collecting the Water Beetles of the Broads district. I have 
noted many other facts than those to which I have referred, 
but I am not at present in a position to interpret them, and 
without interpretation facts are often very trivial things. 
I hope, however, in the course of time to be able to make 
more complete statements on the various points upon which 
I have touched, and to be able to add a few sound facts to 
our knowledge of the subject of bionomics. 
