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(Rud.), and Prosorhynchus aculecitus (Odhn.) have never been met with. 
Five of these species are plentiful on the Norwegian coast and at least 
two have been obtained from the coast of Belgium. The reason for 
their absence from the Scottish coast is to be found in the fact that 
their hosts are absent, in some cases the final host, in others the 
intermediate. Labrus berggylta , the chief and almost the only final 
host of the Peracreadium species, does not occur on the East coast of 
Scotland and probably in this case the absence of the parasite is 
correlated with the absence of its definite host. The same applies to 
Lebouna alacris (Lss. nec. Nicoll 1909), which occurs only in the 
Labridae. This can hardly be the case with Helicometra pulchella, 
however, for it parasitizes many hosts, some of which are not uncommon 
in the North Sea. Here we probably have to reckon with the absence 
of the intermediate host. In the case of the Prosorhynchus species, 
I have not had an opportunity of examining a sufficient number of 
congers, the specific host of the parasite, to express any opinion. 
It was partly with the view of gaining some information on this 
matter that the work at Millport was undertaken. The six species 
above mentioned were obtained there, mostly in great abundance, and 
are now recorded for the first time from British fishes. An attempt 
(Nicoll and Small, 1909) was made to discover the larval forms, in the 
course of which several of the common invertebrates were examined, 
but without success. 
My main object was to examine several species of fish which could 
not be readily obtained from St Andrews Bay and to institute if 
possible a comparison between the parasitic fauna of the East and 
West coasts. As to the latter, the insufficiency of the material hardly 
admits of a just comparison, although in a certain proportion of cases 
such a comparison is not altogether impossible. As at St Andrews 
most of the widely distributed European species were met with ; in 
many cases they are recorded here from new hosts. Most of these 
forms, e.g. Hemiurus communis (Odhn.), Hemiurus luhei (Odhn ), 
Derogenes various (Muller), Zoogonoides viviparus (Olsson), Lecithaster 
gibbosus (Rud.) and Leioderma furcigerum 1 (Olss.) occur in fishes both 
from deep and inshore water. 
The equally widely-distributed Podocotyle atomon (Rud.) occurs 
only in littoral fishes. On the East coast several hundred deep-water 
1 The distribution of this species, however, is possibly not so widespread as might 
have been expected, for I have failed to obtain it on the South coast of England (Aug.— 
Sept. 1909). 
