of the Fishery Board for Scotland. 



211 



On the Structure of the Tail in Myxine (Glutinous Hag). By 

 Professor Cleland, M.D., LL.D., F.RS., University of Glasgow. 



In making a maceration of a specimen of Myxine ghitinosa, one of a 

 number which I owe to the kindness of Professor M'Intosh, I had the 

 satisfaction of laying bare a remarkable structure in the tail, which 

 appears to have hitherto escaped notice, viz., a triangular plate of cartilage, 

 about half an inch in length, placed beneath the end of the sheath of the 

 notochord. The fore end of the plate is about an eighth of an inch in 

 depth, and at its lower end supports a small bifricating process ending 

 quickly in two minute dilatations which abut against the hindermost pair 

 of mucous glands. The inferior margin is prolonged into about twenty- 

 four longer or shorter rays or processes. These extend a certain distance 

 into the inferior fin-rays of the tail, which otherwise are quite similar to 

 the superior rays, consisting of mere fibrous bands. 



Having reference to the disputed position of the Cyclostomata, it 

 appears to me that the structure of the brain, long ago studied by 

 Johannes Miiller, can leave no doubt, when taken into consideration with 

 other characters, of their affinity to the Elasmobranchs. I am inclined, 

 therefore, to consider the plates of cartilage in connection with dorsal 

 fins, as in the case of AcantJiias, developments throwing light on this 

 inferior plate ; and, further, to see in this structure the inferior lobe of 

 the heterocercal tails of the sharks, and the infra-cordal portion of the 

 tails of osseous fishes. 



When we study the tail of a perch or a salmon we find that although 

 the apparently homocercal form of its adult condition is in reality hetero- 

 cercal, the notochord having been directed toward its upper edge, yet, in 

 an embryonic condition, the notochord passes straight back, and is 

 surrounded, with supero-inferior symmetry, by a cutaneous fin exhibiting 

 delicate fibrous rays. This resembles the apparent condition of the tail 

 of Myxine ; but the cartilaginous plate now described may be regarded as 

 showing a tendency to the second stage of tail-development, in which the 

 inferior lobe exhibits special growth. 



On the Eggs and Young of Food and Other Fishes. 



The observations on the development of the Food Fishes — just com- 

 menced at the date of the last report — were carried on chiefly by Mr 

 Edward E. Prince, up to the second week in September, and a large 

 amount of material has been accumulated on the subject. A preliminary 

 report of his able and beautifully illustrated researches was communicated 

 to the meeting of the British Association at Aberdeen * (Section D. 

 Biology). The labour involved in such a task, especially in regard to 

 the manipulations of the microscopic slides of eggs and embryo-fishes, 

 makes the preparation of the complete results with drawings a compara- 

 tively slow process. We hope, however, to be able to communicate 

 these researches to one of the societies before long. 



Detailed study of the following species, with pelagic eggs, has been made : — - 



Cod, emerged from the egg on the 9th day, lived till the 17th day. 



Haddock — 1st series „ „ 20th „ „ 27th „ 



„ 2d series „ „ 10th 



Whiting „ „ « l^th 



Orey Gurnard— 1st series „ „ 13th „ „ 24th „ 



„ 2nd series „ „ 6th 



Common Dab — 1st series „ „ 13th „ „ 24th „ 



„ 2d series „ „ 7th 



Common Flounder „ „ 11th „ „ 24th „ 



Bockling (5-bearded) „ „ 7th 



* Vide 'Report of the Brit. Associat. Aberdeen, 1885.' Section D. 



