302 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Such sudden changes of temperature as a warm blooded 

 animal must accustom itself to are as a rule not 

 experienced by fishes, for changes in the temperature of 

 even a small mass of water such as a pond take place 

 much less rapidly than corresponding changes in the 

 atmosphere. Nevertheless, there are circumstances in 

 which the water temperature may change fairly rapidly 

 — such as, for instance, would be produced by the quick 

 migration of a fish from one part of a small stream into 

 another, or into a pond ; or, perhaps, by a sudden freshet 

 in a small stream produced by cold rain or melting snow. 

 Still more would such change be experienced by fishes 

 living in captivity as for instance in fish-breeding estab- 

 lishments ; and it is chiefly in relation to fishes living in 

 these conditions that catarrh of the skin has been observed 

 and studied. 



These Manx salmon parr were then probably suffer- 

 ing from some kind of dermal catarrh. Indeed I can 

 suggest no other explanation of the lesions observed. 



The other apparent cases of dermal catarrh observed 

 were in several dabs (Pleuronectes limanda) which have 

 been taken during the last year or two. One fish brought 

 to the Piel fishermen's classes in April, 1906, by Capt. 

 Wignall showed the condition very well. The fish was 

 a mature male with ripe testes and apparently in normal 

 condition. But on either side near the tail was a soft, 

 white, slightly translucent tumour not unlike those 

 described from the Manx salmon parr. The tumour had 

 a papillated surface, was about 1 cm. in diameter, and 

 about 2 mm. in height. In the fresh condition there was 

 an irregular radiate arrangement of blood capillaries 

 infiltrating its mass. Smears from a part of this growth 

 were made and stained by Komanowsky's method, and 

 also by Heidenhain's iron haematoxylin. The blood of 



