SEA-FISHERIES LABORATORY. 211 



Melanotic Sarcomata in Skates (Raia batis). 



Several interesting cases of this condition may be 

 recorded. On October 15th, 1912, Mr. T. It. Bailey sent 

 me part of the wing of a skate affected by a sarcoma. 

 The growth occurred on the dorsal surface of the left 

 wing. It was very nearly circular in shape and very 

 Hat, so that it looked like a large pigment patch. On 

 closer examination, however, it was seen that the growth 

 was slightly raised up — one or two mm., and that it 

 was surrounded by an area of pigmentation fading rather 

 quickly into that normal to the skin of the fish. 



On 25th October, Mr. Bailey sent me a further 

 specimen which illustrates the condition of melanotic 

 sarcoma production better than any specimen I have 

 yet seen. The fish was caught by a liner off the coast 

 of Ireland, 45 miles N.W. from " Rathlm-a-Milley," 

 in TO fathoms depth. It was a skate measuring about 

 150 cms. (nearly 5 feet) across the body. The wings only 

 were sent. The fish was in very poor condition, the 

 flesh being very soft, and the fish thinner than usual. 

 It smelt very strongly of ammonia. Mr. Bailey, 

 however, informs me that this is not uncommon in the 

 case of skates or rays which have gone rather "stale," 

 though I had not noticed it in any specimens of these 

 fish hitherto examined, nor in any skates or rays dissected 

 in the laboratory by the students, fish which are certainly 

 very "stale" at times. This ammoniacal odour occurs 

 only in Elasmobranchs, under decomposition. Doubt- 

 less it is to be related to the fact that urea occurs in 

 relatively large quantities in the blood of these fishes, 

 and this urea may undergo conversion into ammonia 

 compounds. 



The flesh of this fish was full of melanotic tumours. 

 There was a very large one on the dorsal surface close to 



