lOSit 



taclied — and the tiln'c imw ix'soiuliles a (.-lul). Tlic 

 thick end (imiLT or anterior end) soon expaniis still 

 iiKH'c (ti_i;'. '-'AHj. I!) and is liollo-wed int(.) a cu]) sliuiio, 

 tViiiii tlic bottom of which the thin end ((/) of the 

 tilire [iroceeds in the form of a shaft, the fibre now 

 hiiving the appearauee of a hiUiOf/nct. The I)o(l\' is 

 further flattened (tig. oOli, (' and /», and the shaft is 

 more and more reduced, until it tinalh- ln'uds (piile to 

 one side (tig. 306, E) ur disappears, the tibre being 

 now similar to a fiat disl<. In the eonimon Skate the 

 electric elements pass througli all the three stages of 

 development, in the .Sandy liav (Ti'tja fahavda) oidy 

 the first two, in the Starry Ray onlj- the first stage. 

 In the electric elements of a Starry Ray, which 

 are club-shaped but always some\vhat eoneave at the 

 tO|i, tlie two constituents of the muscle tiljre, the sareo- 

 plasnia and tlie rhabdia, are parth' separated from each 

 other. They ha\e gathered at the thick end more 

 densely than in the slender portion of the lilire, and 

 a special layer of sarcoplasma. a so-called electric plate, 

 is interposed at the top, immediately below that part 

 of the sarcolemma where the ner\-e fibrils are inserted. 

 Under this electric plate lies a densely striated mass, 

 consisting jirincipallv of rhabdia, but containing nu- 

 merous muscle nuclei, an indication that a considerable 

 amount of sarcoplasma is present. In the cu])-like 

 (iiilboquet-shaped) elements of a Sandy Ray the stri- 

 ated layer contains far fewer and more scattered muscle 

 cells; and under this part the granular substance (the 

 sarcoplasma) has formed a distinct layer with pro- 

 cesses and alveoli (sponge-like meshes), a so-called 

 alveolar layer. In the common Skate the rhabdia is 

 entirely separated from the sarcoplasma and contains 

 no muscle nuclei. Each electric element thus consists 

 ill this species (fig. 306, E) of three plates (a, h. r), 

 one above another, the outer pair {a and c) being, 

 however, confluent at the margin. With the addition 

 of the secondary growths of gelatinous (/) and fil)rous 

 (s) tissue that extend into and till up the spaces be- 

 tween the electric elements proper and also support 

 capillaries and nerves, we find liere, in the common 

 Skate, an electric apparatus of essentially the same 

 Structure as in the Torjiedo and Electric Eel. On each 

 side of a comparatively firm plate, in section densely 

 striated and originallj- formed of rhabdia, are set layers 

 of sarcoplasma differing in their histological structure. 

 This difference may ])erhaps produce different kinds of 

 electricity. In that case we should here possess an 



analogue to the well-kno\\n galvanic piles. ( )r pei'- 

 haps the electricity ma\' be of the same kind in both 

 la\ers of sarco]ilasma. In the latter cas(i the eh'ctric 

 apparatus of thes(! fishes eori'csponds to an agglomei'a- 

 tion of electrophori. 



The manner in which these organs are em])loyed 

 b\- our common IJays is not yet known. Their elec- 

 tric faeult\- cannot l)e doubted; but thousands of tliese 

 lla\s i)ass througli tlie hands of fishermen without any 

 recorded instance of a human I)eing having experienced 

 an electi'ic shock from one of these fishes. When a 

 Ray feels the resistance f)f the hook, and the fishei'man 

 begins to haul in the line, it first endeavours to cling 

 to the bottom by clasping its pectoral fins round some 

 hard object or tighth- pressing them to the ground; 

 and when it emerges from tlie water, it tries to defend 

 itself b-\' raising the ])ectoral fins as a shield for its 

 bo(h-, bending the tail upwards and forwards, and 

 dealing violent blows witii the latter member. Now 

 the tail of these Rays is so formidably armed with 

 large, pointed spines that these in themselves are a 

 sufficient warning to the fisherman against handling 

 the Ray with the naked hand until he has given it a 

 finishing blow, and hence it may well happen that as 

 a rule he has no o]j]iortnnity of experiencing the elec- 

 tric powers of the fish. Whether the electricit}' is 

 utilised in condjats with otlier inhabitants of the deep, 

 in self-defence or to stun a victim, is also unknown. 

 We know that dolphins (toothed whales) are the worst 

 enemies of the large Rays, Ling and Halibut of the 

 smaller ones; but S.wille-Kext saw dolphins seize 

 Rays by the tail, the very part where the electric or- 

 gans arc situated. From ol)ser\ations in aquaria we 

 learn that the Rays secure their prey by casting them- 

 selves over it with a sudden movement of the pectoral 

 fins, squeezing it under their body, and gliding over 

 it, until it can be grasped with the jaws. In these 

 oi>erations the tail can evidently serve merely as a rud- 

 der to direct the course of the fish. So too, when 

 the Rays swim freely about in the water, propelling 

 themselves by undulating movements of the pectoral 

 fins, the tail can only steer and preserve the ecjuipoise 

 of the body. S.wh.i.i'.-Kent compares the movements 

 of a swimming Ray to those of a wading bird that 

 stretches its long legs behind it in its flight. 



The sj'Stem of the lateral line in the Rays requires 

 a special chapter, though it rather closely resembles that 

 of the HoJocephali. It is gencM-ally far more developed 



