J I 5 Part second. 



Of the order oiPlectognathi with an immobile lower jaw, which is 

 almost confined to the tropics, the Aquarium contains two species. 

 Some, such as the Sea-hedgehog, the Globe-fish and Trunk-fish, 

 will be already known to the visitor from dried specimens in the 

 Natural History Museums; those in the Aquarium are the Sun- 

 fish, Orthagoriscus ("Pesce mola") and the File-fish, Balistes 

 ("Pesce porco", fig. 69). It is unfortunate that the Sun-fish is 

 only to be seen in the Aquarium in summer, and then only seldom 

 and that therefore only few visitors can convince themselves that 

 such a monster really exists. For it does not appear to be a whole 

 fish, but fish-head flattened sideways, with an oval outline; the 

 whole hind part of the fish seems to be absent. Along the back 

 edge runs a narrow, thick fin (the tail-fin, which is kept although 

 the tail itself is absent), from the upper and lower ends of which 

 a larger fin rises up. By the movements of these this swimming 

 head is moved slowly through the water in the tank. In the sea 

 however, it must be able to move more quickly than one would 

 think, for in its stomach are to be found Sardines, Cuttlefish 

 and other agile creatures. In spite of the evil odour which the 

 animal gives out even when still living, it is much prized by zoo- 

 logists, less for itself than for the masses of parasites present in 

 all its organs. — The File-fish, which belongs to the same order 

 owing to its narrow mouth and scanty, large teeth, is normally 

 built, if somewhat short for its breadth. From spring to winter 

 it is a constant inhabitant of the Aquarium. In the summer 

 it is lively, inquisitive and companionable, but its company is 

 sometimes uncomfortable and dangerous for its mates. It was 

 formerly in the same tank with the turtle, but it always snatched 

 away the food from the latter, and when moved to the tank with 

 the craw-fish, it bit their eyes out! When the temperature falls 

 towards iS" C it always becomes indolent, loses its appetite and 

 invariably perishes in the winter. 



In tank Nr. 9 live two small fish, the delicate Trumpeter, 

 Centriscus (fig. 51) with the long beak, and the Cuckoo-fish, 

 Capros (fig. 50). In colour they resemble their companion, An- 

 thias (p. 114) and, although caught in depths of 50 fathoms, they 

 live well in captivity. 



The Cuckoo-fish belongs to the Mackerels which are a family 

 of true free-swimming fish. Almost all members of this group 

 are inhabitants of the open sea, which spend their whole life 

 swimming and drifting and only approach the coasts to lay their 

 eggs. During these periods they are the object of extensive fisheries, 

 more especially the Tunny. It is very difficult to accustom the 

 fish to a life in the Aquarium. They are shy and always in a 

 state of rapid motion and soon knock themselves to death against 

 the walls of the tanks, the Sword-fish even dying as soon as it 

 is taken out of the water. Besides the Cuckoo-fish, only one small 



