ELECTRIC TISSUES, TELEOSTS 115 



seen in the latter parts of the development is the longitudinal striation or 

 fibrillation (Fig. 108, C). Earlier in 

 the process the cross striation is the 

 most prominent. Each bundle of 

 fibers develops into one of the col- 

 umns of the completed electric or- 

 gan. In changing its longitudinally 

 placed sarcoblasts (they might more 

 properly be called electroblasts) into 

 electroplaxes, they are changed 

 from the vertically elongated form 

 into a horizontally elongated form 

 without changing in the least their 

 morphological position or axes. The 

 selachian fishes thus show a com- 

 plete homology in their electro- 

 plaxes. Unfortunately we do not 

 know the embryology of the more 

 numerous teleostean forms. 



Technic. The use of nitrate of 

 silver by the Golgi method has been 

 carried even into the embryonic 

 tissue, although without the decided 

 results that it has yielded in the 

 adult tissue. Methylene blue has 



not been successfully used in any electric tissue with the exception of 

 Raja by Retzius, who, however, has neglected to announce the secret 

 of his success, if there be any secret that can be stated. 



LITERATURE 



OGNEFF, J. " Uber die Entwicklung des electrisches Organs bei Torpedo," Arch. f. 



Anat. u. Physiol., 1897, S. 270. 

 EWART, J. C. "Development of the Electric Organs in the Skate," Phil. Trans. Roy. 



Soc., Vol. CLXXIX B, p. 399. 

 ENGELMANN, TH. W. "Die Blatterschicht derElek. Organe von Raja in ihren genetischen 



Beziehungen zur quergestriften Muskelsubstanz," Pfluger's Archiv, Band LVII, 



1894, S. 149. 



FIG. 108. A-C. Three steps in the histo- 

 genesis of an electroplax of Tetronarce, the 

 "torpedo" or "numbfish." The body of 

 the electroplax is derived from the pos- 

 terior end of the fiber instead of from the 

 anterior, as in Raja. (After OGXEFF.) The 

 weak stria represent the fibrillation rather 

 than the cross striation of muscle. 



THE ELECTROPLAX IN TELEOST FISHES 



The teleost fishes present a number of examples of electric tissues 

 which are, with one exception, recognized to be modified muscular tissue 

 upon anatomical and histological grounds. Unfortunately the embry- 

 ology and histogenesis of these organs has not been investigated for 

 lack of material. This is especially unfortunate in the case of Malap- 



