206 PROCEEDINGS OP THE ROYAL, SOCIETY OP QUEENSLAND. 



healthy fish-life. Bacterial nialaches of fish are commonly 

 associated with Saprolegnia attack, and Shelfoixl (1918c, p. 

 4G) has stated that excessive acidity due to COg probably favours 

 the development of this destructive fungus. 



(d) Bacteria as a Possible Cause. 



Almost the whole of the diseased material was already 

 dead at the time of our examination, and as putrefactive 

 changes had taken place a bacterial exploration under field 

 conditions would probably have been of little value. Though 

 bacteria were found in various tissues, the possibility of a 

 bacterial disease being the cause of the epidemic had not 

 been provided for by us, and as a consequence cultures were not 

 able to be made on the occasion of our only visit to a localitj^ 

 in which the epidemic was present. 



Several bacterial diseases of fish are loiown, the most 

 destructive being probably that which has at different times 

 caused heavy mortality amongst salmon. The so-called 

 " salmon disease," wliich was formerly attributed to Sapro- 

 legnia, has been shown by J. H. Patterson in his Parliamentary 

 Report, Fisher}^ Board for Scotland (1903), to be due to a 

 diplobacillus, Bacillus salmonis pestis. Additional information 

 Avas given by Drew (1909). [See also Hofer, pp. 19-22]. Marsh 

 had previously (1902, 1904) described Bacterium truttce, a 

 pleomorphic organism, sometimes assuming the form of a 

 coccus, or a bacillus, or a diplobacillus, wliich was found to be 

 fatal to various kinds of trout in the United States. 



Hofer (1906) gave a summarised account of the various 

 bacterial diseases described as occurring in freshwater fish in 

 Central Europe, the causative organisms being Bacillus 

 salmonicida. B. pestis astaci, B. cyprinicida, B. anguillarum, B. 

 vulgaris, B. piscicidus, B. piscicidus agilis, and a few others. 



Grieg Smith (1900a) described one as B. piscicidus bipolaris, 

 which was found to be fatal to certain marine fish in New South 

 Wales ; and also another (1900b) called by him Vibrio hresimce, 

 which destroyed marine bream in that State. 



7. IS IT DUE TO MORE THAN ONE CAUSE ? 



The epidemic nature of the Queensland disease, the 

 apparently rapid course wliich it runs, and the particular 

 susceptibility of certain species, all suggest that the malady is 



