TRANSACTIONS OF SECTION B. DEPT. ZOOLOGY AND BOTANT. 593 



In spite of Professor Babuchin's and of Dr. Sachs' exertions, tlie development 

 of Malopterurus and of Gymnotus unfortunately is still wrapped in mystery. Pro- 

 fessor Babuchin, however, conlidentl}' extends his law to Malopterurus, as the size 

 of Bilharz' electric plates varies in proportion to the size of the fish. 



In my work on Gymnotus/ b)' combining the results of former observers with 

 those of the lamented Dr. Sachs, I have proved the number of colunuis to be the 

 same in large and in small specimens, again taking into account individual varia- 

 tion. Professor Fritsch has confirmed this statement by a new and careful census 

 of the columns in several specimens widely differing in size.^ 



It is not my intention on this occasion to enter upon the many important 

 inferences which maj^ be drawn from delle Chiaie's and Babuchin's law. This law, 

 indeed, has become a leading ftict in the physiology as well as in the embryology 

 of the electric organs. For instance, an obvious conclusion from it is the following. 

 The number of electric plates remaining the same, and their thickness only increasing 

 with the size of thje fish, whilst the electromotive force of the discharge also increases, 

 the difference of potential engendered by every plate is evidently proportionate to 

 its thickness. Now, as the difference of potential does not depend upon the size of 

 the bodies by whose reciprocal action it is produced, we are unavoidably led to 

 conclude that in a thicker electric plate there is a i-epetition, and consequently a 

 multiplication, of the difference of potential in proportion to its thickness. 



But my wish here is to direct the attention of the Section to the part which 

 delle Chiaie's and Babuchin's law seems destined to play in the systematic distribu- 

 tion of the Torpedinidfe. According to it, the number of columns in the electric 

 organs of a species of Torpedinidse, is, from a certain stage of its development, a 

 given one. This number may be the same, or nearly the same, in distinct species 

 of Torpedinidse. But if, in two specimens which do not otherwise show very mai-ked 

 specific characters, the number of columns differs more than the range of individual 

 variation fairly permits, the .specimens ought to be pronounced specifically distinct. 

 In other words, the average number of columns ought, henceforward, to form part 

 of the diagnosis of a species of Torpedinidse. 



Hitherto this point has been entirely overlooked by zoologists. Elaborate papers 

 were published on the system of the Torpedinidfe," in which the number of the 

 columns is not even mentioned. The whole literature on torpedo from Hunter's 

 time down to Professor Fritsch's new researches, did not comprise more than six- 

 teen enumerations of columns, on only fourteen specimens.^ They were all of them 

 made, as it was understood at the time, on common European species, T. manno- 

 rata, occllata, Galmnii, excepting one, by Professor Henle, on his Narcine (now 

 Astrape) dipterygia, from the South Sea. This species offered the unusually small 

 number of 130 columns. The other species yielded numbers ii-om about 300 to 

 about 500, excepting, however, one of two very large torpedines, of 4 ft. in 

 length and 50 lbs. weight, which in 1773 were caught off Torbay, and examined 

 by the illustrious John Hunter. He counted 1,182 columns in one of their organs. 

 As he had counted 470 columns in one of the organs of an 18-inch specimen of 

 the common torpedo, and as he took for granted that these huge torpedines were 

 simply older individuals of the same species, he by this single observation was led 

 to tlie erroneous conclusion that the columns increase, ' not only in size but in 

 number, during the growth of the animal, new ones forming perhaps every year on 

 the exterior edge, as there they are mucli the smallest.' This process, he a'dds, may 

 be similar to the formation of new teeth in the human jaw, as it increases; and for 

 more than sixty years this bold assumption of Hunter's has reigned undisputed in 

 all the text-books of zoology and physiology. 



Hunter, however, could not have chosen a less felicitous illustration. After a 

 certain stage of development is over, new columns form as little in the electric 

 organ of torpedo as new teeth in the human jaw. The true conclusion to be drawn 



' Dr. Carl Sachs' Untermehvngcn am Zxttcraal, Gijmnofvs clrctricug, nach semem 

 Tode hcarhntct von E. du Bois-Reymond. Mit zwei Abhandlungen von G. Fritsch. 

 Leipzig, 1881, pp. 81, 32. 



- L. c. pp. :!6]. 393. ' Z. c. p. 401. 



1882. Q Q 



