154 KEPORT— 1888. 



nerves, and gave me an idea of the minute structure of the electric 

 plates. Of Wagner's ' bouquet,' a name which well denotes the appearance 

 presented by the remarkable behaviour of the nerves before entering the 

 plates, and of the beautiful ramifications of the branches on the plate 

 itself, I made preparations, which, however, do no more than confirm the ob- 

 servations of Ranvier. The final terminations of the nerve-twigs were well 

 brought out by the gold and silver methods, the former giving a positive 

 and the latter a negative picture of the tei'minal nerve-branchings. On 

 the disputed point as to whether the twigs from neighbouring branches 

 communicate so as to form a network, my preparations throw some light. 

 In many places a distinct network is visible, although very commonly 

 the reticulation is only apparent, observation by means of a high power 

 and more exact focussing showing a want of continuity. It is quite 

 possible, however, that the want of continuity in these places is due to rup- 

 ture of the network during the treatment or to unequal action of the stain. 



The ' Punktirung ' of Boll, corresponding to the ' Palisade ' of 

 Remak and the ' electric cilia ' of Ranvier and Ciaccio, and of such 

 doubtful significance, is well seen in my gold preparations, being repre- 

 sented by numerous violet-coloured points regularly disposed on the 

 terminal nerve-branchings. I am sorry that I have not yet had time to 

 make a careful examination of transverse sections of the ' electric plates,' 

 which would reveal the httle rods or ' Stabchen ' of which the ' Piinktchen ' 

 are the inferior ends. I further regret this, as I might have been able 

 to express an opinion as to the nature of the intermediary layers of the 

 plate, in which Krause mentions the presence of sinuous fibres. 



The organ in the rays, which must now be regarded as electric, 

 although functionally it is not of such importance as the corresponding 

 structure in other electric fishes, would appear to be represented in all 

 the members of the group. I have found it present in the species Raia 

 clavata, R. batis, R. oxyrhyncJms, R. oniraletus. Couch (=iJ. circulans. 

 Day), in all of which it is large and well developed, and in R. radiata, in 

 which it consists of a small slender cylinder. It was first noticed in 

 R. clavata by Stark (1844) and was later described by Robin in R. clavata, 

 R. ruhus, and R. batis, while Professor Ewart, iu a series of papers read 

 quite recently before the Royal Society, gives an account of the develop- 

 ment of the organ in the species R. batis, R. fullonica, R. circularis, and 

 R. radiata. The form which occurred most commonly at Naples was 

 named R. asterias in the Aquarium Catalogue, and is evidently identical 

 with our species R. clavata. Making use of this form, I employed my 

 time in going over some of the ground already traversed by Robin in 

 following out the nerve-supply and general relations of the organ. The 

 results compared with the condition observed in the torpedo, and briefly 

 stated, are these : — The organ is long and cylindrical in form, and taper- 

 ing both anteriorly and posteriorly; it occupies a position on each side 

 of the tail for the posterior two-thirds of its length. Its origin is in the 

 centre of the sacro-lumbar nauscle, which after the appearance of the 

 organ gradually ceases, the electrical apparatus in like gradual manner 

 taking its place. Indeed, embryological research shows that the electrical 

 organ arises from a transformation of this muscle, in which the con- 

 tractile substance has undergone a change. It reaches its maximum 

 diameter about the beginning of the first dorsal fin, and after continuing 

 of uniform thickness for several centimetres it gradually diminishes 

 towards the tip of the tail, into which it, however, extends. In the 



