xi ELECTRICAL FISHES 393 



of the adductor (Vetter, "Kiemen- u. Kiefer-muskulatur der Fische," 

 Jenaische Zeitschr. VIII.). 



As regards the developmental processes of the electrical 

 organs, it is a priori improbable that the number of separate 

 elements (plates or columns) should increase with the growth of 

 the individual. Even in 1839 it was affirmed by Delle Chiaje 

 " that the columns of the electric ray grow by intussusception 

 (the same number being developed as exists in miniature in the 

 embryo), merely by gradual increase in mass and size." R. 

 Wagner in 1847 defended this statement against Valentin and 

 Babuchin, extending it to the number of plates in the columns, 

 and tracing it back to its embryological origin. This dictum of 

 the preformation of the electrical elements makes the number of 

 columns (and plates) in different individuals of the same species 

 of electrical fishes to be approximately the same, whether the 

 animals are examined young and small, or when fully developed. 



Du Bois-Keymond (4 e, p. 403) put together in the following 

 table (Table I.) all the estimates then made of the columns in the 

 electrical organs of Torpedinidce. 



In these the calculation from the foetus of Torpedo ocellata 

 speaks very decidedly in favour of the above conclusion. The 

 anomalous and divergent results of Valentin and Girardi, however, 

 leave an uncertainty which at first drove du Bois-Reymond 

 also to the conclusion " that the deposit of columns in different 

 individuals of the same species was initially different, and did not 

 alter subsequently." Marked deviations in number of columns, 

 exceeding the range of individual variations (such as the cases 

 cited by Hunter and Henle in the above tables), would of course, 

 on the preformation theory, be ascribed to difference of species. 

 Fritsch took the trouble to review the family of Torpedinidce 

 from this standpoint, and the following data (Table II.) give 

 some examples from his numerous calculations (Fritsch, 12). 



[TABLE 



