J. S. Dunkerly 
329 
are more restricted in occurrence. One case is that of Sphaeromyxa ovata 
which occurred in all of the three specimens of Onos tricirratus examined, but 
in only one of 46 specimens of Onos mustela which came from the same locality. 
In the one case in which it did occur, it was present in very small numbers 
only, as though it had not been able to establish a strong infection. It has 
been held that these spores are abnormal spores of Sphaeromyxa balbianii, 
but the spores are very dissimilar and were not found together by me. Another 
example of restriction in distribution is shown by Myxidium incurvatum , 
which was found in five out of 19 specimens of Blennius pholis , but not 
in one of 30 specimens of Gobius (various species) taken from the same rock 
pools. Yet Myxidium incurvatum is found in a large number of different 
hosts, and the Gobies must sometimes take up spores of this and other species. 
It can be suggested at least that not all species of fish are equally susceptible, 
and it appears likely that some species of Myxosporidia are specific to certain 
hosts, but their mere occurrence in different hosts cannot be taken as proof 
of specific difference, without some accompanying difference in form, size of 
spore, or other characteristic feature. Therefore it will be found that in this 
paper specimens have been identified as far as possible with pre-existing 
species, and also as far as possible with the species mentioned by Labbe in 
Das Tierreich. It would be a convenience to parasitologists if in the case of 
parasites a trinomial system of nomenclature for animals and plants could 
be used, indicating the specific character of the parasite and also the host 
from which it was obtained. 
In the following list the fish hosts have been named for the sake of uni¬ 
formity according to Dr Smitt’s edition of Fries, Ekstrom and Sundevall’s 
Scandinavian Fishes. 
Host 
Examined Negative 
Infected Parasite 
Agonus cataphractus 
2 
2 
0 
Anguilla vulgaris ... 
1 
1 
0 
Blennius gattorugine 
5 
5 
0 
Blennius ocellaris ... 
2 
1 
1 
Myxidium incurvatum Thel .+Cerato- 
myxa arcuata Thel. 
Blennius pholis 
19 
14 
5 
Myxidium incurvatum Thel. 
Bothus maximus ... 
14 
13 
1 
Myxidium incurvatum Thel. 
Callionymus lyra ... 
15 
0 
15 
Myxidium incurvatum Thel. (13). 
M. incurvatum -f Ceratomyxa arcu¬ 
ata Thel. (2). 
Capros sanglier 
1 
0 
1 
Ceratomyxa lata sp. n. 
Clupea pilchardus ... 
17 
6 
11 
Plasmodium only (1). Ceratomyxa 
truncata Thel. + Coccomyxa morovi 
Leger and Hesse. 
Cottus bubalis 
3 
0 
3 
Ceratomyxa dubia sp. n. (3). Plisto- 
phora typicalis Gurley in liver (1). 
Chloromyxum quadratum Thel. in 
muscles (1). 
Gadus luscus 
... 6 
6 
0 
