Io6 Part second. 



quently. The electric organ is used both defensively by the Torpedo 

 and also for killing or at least numbing its prey. A young specimen 

 is always kept in a small open tank, in front of tank Nr. lo, for 

 visitors to try the electric power of the fish. The Torpedo lames 

 and kills its prey by these shocks ; it makes use of a physical means 

 where the sea-anemones and the Octopods use chemical means, 

 through their sting-cells and salivary-glands respectively. The 

 victim on which the Torpedo prefers to use its noiseless hghtning 

 is the mullet (Mugil, p. 114). Whenever it sees such a fish approach- 

 ing it rises from the mud on which it is usually lying and throws 

 itself against the victim. Overcome half by fright and wholly 

 by the electric shock the poor mullet falls to the ground and is 

 swallowed. The Electric Ray is one of the most common fishes 

 of the Bay of Naples and in spite of its poor flesh is often brought 

 to market. They bring forth living young ones, 8 — 14 at a time. 

 The very young embryos have still the spape of sharks and only 

 later on become flattered and disk-shaped. 



Of the other Rays the Skate, Raja (fig. 67), and the Sting-ray, 

 Trygon (fig. 62), are found in the Aquarium, but the latter more 

 rarely. The former have a lonzenge-shaped body of brown colour, 

 and a tail armed with a number of small spines. They lay their 

 eggs in capsules, which are cast .ashore on the beach of the North 

 Sea and are called Skate-barrows. Tlie Sting-rays are of dark 

 violet colour and have a long slender tail. The latter bears a 

 strong spine which is in connection with a poison gland. It can 

 cause painful wounds which are fatal to other fish. The young 

 are brought forth living. 



The fish is the type of swimming animal. Although there are 

 animals which swim in almost all other classes, from the lowest 

 up to the mammals, yet the conception of a swimming animal 

 is embodied in fishes. Fishes can only move from one place to 

 another by swimming and that are no fishes which cannot swim. 

 From this arises the popular use of the word fish, applied to animals 

 which are not fish at all, such as the devil-fish, cuttlefish, cray-fish 

 and jelly-fish. While in many swimmers in other classes of the 

 animal kingdom the swimming organs are limbs or other processes 

 of the body, in almost all fish the sole locomotory organ is the 

 muscular trunk (especially the hinder part) which drives the 

 animal through the water by its wave-like movements. The fins 

 act as keel or rudder alone. The Skates form an exception to this 

 rule, moving by wave-motions of the side-fins, the body being 

 stiff — the Sea-horses form another exception (p. 112). Now 

 there are many fish which make little use of this capability of 

 swimming but spend their lives on the floor of the sea, where 

 they lie on the sand or mud in wait for their prey and only seldom 

 swim around. These are the Bottom-fish. We have already 

 met a number of them among the Cartilaginous fishes and will 



