122 The Irish Naturalist July, 



May I add how pleased I shall be if Irish naturalists will assist in the 

 rapid completion of the Conchological Society's Census of Distribution, 

 by permitting me to see slugs and snails from every part of Ireland, for 

 wliich part of the kingdom the blanks still to be filled up are very 

 numerous. 



W. Denison Roebuck. 



J59 Hyde Park Road, Leeds. 



Fish Diseases. 



Two important contributions towards our knowledge of hsh diseases 

 published within recent years in Ireland have not yet been alluded to 

 in the pages of the lyish Naturalist. The lirst of these is a paper by 

 L. von Betcgh of Fiume in Austria on yolk-sac dropsy (Hydrocoele 

 cmbryonalis. Fisheries, Ireland, Sci. Invest., 1913, iii. [1913])- This 

 epidemic disease affects trout alevins in fish-breeding establishments. 

 It appears very suddenly, and first attracts attention by the swollen 

 yolk-sac which seems to weigh down the little fish, which drops to the 

 bottom of the hatching tank. Later on the yolk-sac bursts and the fish 

 dies. The disease is due to bacteria {Diplobacillus liquefaciens piscium) 

 but no remcd}'^ has as yet been discovered to combat it. 



The second paper (A. E. Mettam — Report on the outbreak of Furunculosis 

 on the River Liffey in 1915, Fisheries, Ireland, Sci. Invest., 1914, 

 li. [1915]) deals with a disease known as furunculosis, which produces 

 abscesses or boils in freshwater fish. A serious outbreak of this disease 

 occurred some years ago in the River Liffey among salmon. Prof. Mettam 

 now describes the nature of the disease which he traces to Bacillus 

 salmonicida. It is probably the same ailment which was investigated 

 by Dr. E. J. McWeeney many years ago. The most obvious remedy to 

 prevent the undue spreading of such disease is to remove any affected 

 fish from the water and destroy them. Great care should also be taken 

 when introducing fish eggs or fry from places where this disease is known 

 to exist. 



Some Migrant Notes. 



Under above title Mr. J. P. Burkitt (p. 103 ante) gives his observations 

 of Spring Migrants for a series of years. It is well-known that such 

 average would only apply to a certain district and, as a rule, be earlier 

 the more southerly the locaUty. Appended is a table drawn up from 

 my observations here, and it may be well to state that my " average 

 date " is the mean of the earliest and latest dates of first appearance 

 (this .sometimes gives a misleading impression as to the usual date of 

 arrival), and that in the " variation from average "-|- indicates the number 

 of days later than average of first observation and — the number of days 

 earlier. During the past 15 years my notes show that the song of the 

 Chaffinch has first heard from 17th January till 23rd February. 



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