18 
other and from other fishes. And yet in the salmon we have 
a fish which passes half of its time in fresh water, and half in 
salt water, and can breathe and enjoy life equally well in 
either ; whilst to the great majority of sea fishes contact with 
fresh water is instant death ; and the salmon itself would be 
suffocated if buried in the slime and mud, which is the 
chosen abode of the eel. I here offer you another topic 
deserving the most careful and painstaking microscopical in- 
vestigation.” Mr. Lee then described, at some length, many_ 
of the parasites which were found adhering to the gills and 
other portions of various fishes. Amongst others he men- 
tioned the cruel-looking Lerneonema Spratta, which burrows 
deep into the eye, and sometimes into the body, of the sprat ; 
Chondracanthus Zei, which is found only on the gills and gill- 
plates of the dory; Nicothoe Astaci, which is peculiar to the 
branchie of the lobster; and Bopyrus Squillarum, _ which 
attacks the prawn, getting beneath its carapace, and giving it 
the appearance of a person with a badly swollen face. ‘‘ Of 
these,” he said, ‘‘I have specimens on the table ; but I will 
take, as typical of their class, for brief description, the three 
entomostracous parasites of the salmon. Adhering to the 
scales of a salmon, generally on the belly and near the vent, 
may often be seen a brown-looking crustacean from half to 
three-quarters of an inch in length, and somewhat resembling 
in shape the great limulus, or ‘king-crab.’ This is commonly 
known as the ‘ sea-louse’ (Lepeoptheirus Stromii), as it is only 
on salmon coming up from the sea that itis found. On another 
salmon may possible be seen argulus foliaceus, the little green 
flat creature with two leaflets to its tail which attacks every 
freshwater fish, and which you may see turning somer- 
saults, and performing the funniest antics in the tanks at 
the Zoological Gardens—especially that in which the perch 
are kept. This is known as the ‘river-louse,’ and is not 
found in salt water. Adhering to, or rather fixed in, the gills 
—often in considerable numbers—is a third parasite, called 
by fishermen the ‘ maggot ;’ and from the presence or absence 
of these parasites some have endeavoured to discriminate be- 
tween a ‘fresh-run’ and a ‘foul fish.’ The presence or 
absence, however, of either of the parasites of the salmon is 
not a true test of the condition of the fish. My own investi- 
gations lead me to believe that neither of these parasites cause 
disease or injury to their hosts, although sickly and diseased 
fish are more exposed than healthy ones to their attacks, 
because they are less able to avoid them. Fish, like human 
beings, when sick, are disposed to remain still and inactive, 
and at such times these agile little swimmers are enabled more 
readily to approach and attack them. The supposition was 
