The Origin of the Electric Organs in Astroscopus Guttatus. 171 



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Lappens von Torpedo. Morph. Jahi-b., XXXI, 104-115. 



87. Stark, J., 18-14, On the existence of an electrical apparatus in the flapper skate and 



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 Bohm. Ges. d. Wiss., Math.-nat. CI., No. XV. 



89. Silvester, C. F., 1904, The blood vascular system of the tile-fish, Lopholatilus chamse- 



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91. Waller, A. D., 1899, Thierische Elektrizitat. 



92. Walsh, 1773, Phil. Trans. Roy. Soc. London. 



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95. WiNTERSTEiN, 1914. Han<lbuch der vergleichenden Physiologie. 



EXPLANATION OF PLATES. 



I. 9.5 mm. embryo, X250. Diagrammatic anterior view of eyes to show relation of 

 electric tissue (stippled) to eye-muscles. 



R. Ex llectus externua muscle. O. Inf Obliquus inferior muscle. 



R. Int Rectus internus nauacle. O. Sup Obliquus superior muscle. 



R. Inf Rectus inferior muscle. Ex. C External carotid artery. 



R. Sup Rectus superior muscle. 



II. 20 mm. embryo, X200. Diagrammatic anterior view of eyes to show increase of 

 electric tissue (stippled) and relation of cranial nerves to eye-muscles. 

 Roman numerals indicate cranial nerves. 



III. 20 mm. embryo, X475. Diagrammatic median view of left eye. 



IV. 33 mm. embryo, X200. Diagrammatic anterior view of eyes to show relation of 



nerve III to eye-muscles and to the four separate electric organs (stippled). 



To left is shown the electric branch of nerve III and to right the oculomotor 



branch. 

 V. Rectus internus muscle. Fom- stages to show gradual gro^vth and differentiation of 



electric tissue on the young muscle. 

 Fig. 1. 4 mm. embryo. Cross-section. Electric area slightly darker than muscle 



area. 

 Fig. 2. 9.5 mm. embiyo. Cross-section. Electric area increased in size and 



staining capacity. 

 Fig. 3. 14 mm. embryo. ObUque section. Electroblasts multinucleate. 

 Fig. 4. 20 nmi. embryo. Cross-section showing only a portion of the electric 



area. Electroblasts vacuolated. Myoblasts striated. 



El Electroblast, multinucleate. Un. N Undifferentiated nucleus 



M Myoblast. _ of electroblast 



V Vacuole. N Nucleus of myoblast. 



S Striations. 



VI. Pilectroplaxes. Three stages to show giowth and differentiation of adult electroplax 

 from single electroblast. 

 Fig. 1. 20 mm. embiyo. Single electroblast. Longitudinal section to show 

 formation of ventral papillae from vacuoles. Nuclei undiffei^entiated. 



El Electric area of electroblast. Un Nu Undifferentiated nucleus. 



N Nutritive area. S Striation. 



D. V Dorsal vacuole. P Papilla. 



V. V Ventral vacuole. 



Fig. 2. 33 mm. embryo. Longitudinal section of electroplax. Nutritive and 

 electric areas differentiated. Stiiations straight and regular. 



El. Nu Electric nucleus. N. Nu Nutritive nucleus. 



