OF THE NORFOLK BROADS. 
35 
stage which at present we are most ignorant about, and it 
is this stage which the Biological Station on the Broads 
ought to be of great assistance in helping to clear up. 
Mr. Balfour Browne has sent me during the year 1904 
several hosts, such as Corixa and Notonecta, with larvae 
of the Water mites attached, which have always turned 
out to be the larval forms of the genus Hydrachna. I have 
myself found on the Broads the parasitic mites A tax Bonzi 
and A tax ypsilophorus in the Fresh Water Mussel, and 
I have also found larval forms of Arrhenurus parasitic on 
a small fish ; but what becomes of the larvae of the other 
mites, such as Limnesia, Piona, Diplodontus, and others, 
has yet to be discovered. 
Some have been found, I believe, in Fresh Water Snails 
( Planorbis ). I have examined some hundreds of specimens 
of this mollusc, but so far have found nothing to record. 
As far as we know, the larvae remain attached to their 
host for about a year, during which time they grow very 
considerably. They ultimately throw off the six legs they 
started life with and hang like little pears upon the legs and 
body of the host. In the spring they break out of the envelope 
which encloses them and become free-swimming, with eight 
legs in the place of the six they first started with. This 
stage, in which they are known as Nymphs, lasts another 
twelve months and is spent in eating and growing. At the 
end of this time they pass into an inert or pupal stage 
from which they emerge adults. They are pale, thin, and 
weak at first, but they soon develop into the beautiful 
creatures they are in shape and colour when fully grown. 
How long they will continue to live when fully developed 
I cannot say, but I have kept some considerably over twelve 
months alive in a window tank. 
The list herewith includes all collections made as far'as 
I know since October 2nd, 1896, when a small collection^ was 
sent to me by a Ouekett friend who had spent his holiday^on 
the Broads. 
Adult forms only have been examined, larvae and Nymphs 
not having been considered for the purpose of this paper. 
