30 THE FISHERIES OF THE ADRIATIC, 



Galvauii), and another species T. narcc. They inhabit exclusively the soft 

 loam-beds in 20-60 fathoms water. 



They are often joined by the Angler, or Fishing Frog (Lophitis pisca- 

 torius), which, however, also frequents shallow waters. 



The young and immature Sharks also inhabit these regions, — probably 

 also the mature ones, although these are rather to be classed amongst the 

 migratory class of fishes. Amongst them the Angel-fish [Rhina squatind), 

 the Spiny Dog-fish [Acanthias sp.), the Spotted Dog-fish [Scyllinm sp.), are 

 the most prevalent ; the Blue Shark (Carcharias glaucus) is rare ; and 

 Centrina Salviani is very rare. 



Class II. — Migratory Forms. 



The migratory or pelagic forms comprise fishes, Cephalopods, Medusae, 

 also some species of Tunicates, and Gasteropods, which plough the deep 

 without fixed abode, and without reference to coast and bed. Their move- 

 ments are determined entirely by the properties of their element, i.e. by 

 the temperature, composition, and depth of water, as also by the amount 

 and quality of the nourishment it affords. They come mostly in dense 

 shoals, and this is the season most propitious for their capture ; others, again, 

 follow these shoals in pursuit of prey. 



They appear near land only during certain months. At other times they 

 are supposed to be in deep water, and perhaps far away. But absolutely 

 nothing is known on the subject, nor is a satisfactory reason given why they 

 approach the land: the idea of their coming for spawning, if not altogether 

 a fallacy, is at all events questionable as regards the majority, whose ova and 

 young are found at a great distance from the shore. 



In the upper strata of water, down to 10 fathoms' depth, Rliizostoma 

 Cuvieri are common, often as much as one metre long, and 40 lb. weight, 

 99s P er cent, of which, however, is water, \ lb. being the actual weight of 

 animal substance when exposed to the air. Less frequently met with are 

 species of Pclagia, Oceana ampullacea (a kind of medusa), Bcro'e citcitmis} 



The members of the Medusa tribe which appear to abound most in the Arctic Seas 



