1902-1903.| Daustribution of the Smaller Crustacea. 13 
and for that matter, to any part of the fish; but the adult is 
never found anywhere except on the gills of the fish, and 
usually on the gills of a Gadoid. It may be that only those 
young Lernwa that happen to attach themselves to the gills 
are able to survive and reach the adult stage, while those 
which become fixed to other parts, finding an environment 
unsuited to the kind of life they have to live, and food 
differing from that which they require, necessarily perish. 
But only a knowledge of the life-histories of these parasites 
will throw light on some of the difficulties that have been 
alluded to. 
Though the examples of restricted distribution I have 
referred to are no doubt interesting, the next example I 
would mention seems to me to be still more remarkable, 
and a reference to it will, for the present, conclude these 
observations. It is the occurrence of what appear to be 
free-living copepods in the nostrils of the cod and of some 
other teleostean fishes, My attention was first directed to 
this peculiar habitat by observing a whitish coloured object 
close to the outer edge of one of the nostrils of a lumpsucker 
_ (Cyclopterus lumpus). This whitish object, on being carefully 
examined, proved to be a Bomolochus, apparently identical with 
Bomolochus solew, Claus, so named from its having been taken 
by Claus on the back of the common sole (Solea vulgaris). 
But though the Bomolochus happened to be first noticed in 
the nostrils of the lumpsucker, it did not appear, from sub- 
sequent examination, to be very common on that fish. I was, 
however, not a little surprised to find that the lumpsucker was 
not the only fish that harboured copepods in its nostrils, but 
that they were also present in the nostrils of other kinds, and 
especially in those of the cod-fish. I have examined a con- 
siderable number of cod-fish since the copepods were first 
observed, and find that they are moderately common in the 
nostrils of that fish, My son has obtained them in the 
nostrils of cod captured in the Irish Sea; and Mr Lindsay 
has also found them in the nostrils of cod he examined, and 
which were caught near the Isle of May. Bomolochus solew 
has now been found in the nostrils of at least six other 
kinds of fishes besides the lumpsucker and the cod—-viz., the 
haddock, whiting, saithe (or coal-fish), ling, plaice, and flounder, 
