THE GYMNOTID EELS OF TROPICAL AMERICA. 165 
Sachs. During one hour this eel gave 150 distinct shocks and by actual measure- 
ment the last was as strong as the first. Humboldt stated that after a few shocks 
the eel became exhausted and it took both food and rest to recuperate its electric 
power. Sachs found no evidence of such a condition. 
The shock of the electric eel readily decomposes potassium iodide, as has 
been shown by its effect on potassium iodide starch-paper. 
3. Origin of Electric Organs. 
Fritsch concluded (Sachs’ Zitteraal, 355 et seq.), after a comparison of the 
musculature of electric eels and the other Gymnotids, that the large electric organs 
have originated through the metamorphosis of the lateralis imus muscles. This 
view is substantiated in several ways. The muscle lateralis imus occurs on both 
sides of the median line in the other Gymnotids in precisely the position occupied 
by the large electric organs in the electric eel, in which this pair of muscles are 
wanting. Along the ventral side of each of the large electric organs is a small strip 
of muscular tissue, which is continuous with the electric plates. This is probably 
an unmetamorphosed remnant of the muscle lateralis imus. The origin of Hunter’s 
and Sachs’ organs has not been definitely worked out. The remaining musculature 
is the same in all Gymnotids. It is known that the electric organs of several of the 
other electric fishes (Torpedo, Malopterus, etc.) are metamorphosed muscle tissue. 
Il. Higenmannia virescens (Valenciennes). 
Sachs (/. c., p. 69) recorded in his notes an observation on pseudo-electric or 
electric tissue in Sternopygus (Eigenmannia) virescens. As this portion of the 
notes was not worked up before his death it is not clearly understood. He wrote: 
“Der dem electrischen Organ von Gymnotus entsprechende Theil zeichnet 
sich durch regelmiissige Streifung in Zwischenriumen von 1™™ aus. Der Durch- 
schnitt hat ein entschieden an Gymnotus erinnerndes Verhalten. Die betreffende 
Stelle (a) ist durchscheinend und von horizontalen Septis durchzogen, Die mikro- 
skopische Untersuchung fallt wegen der Schwierigkeit des Gegenstandes unge- 
nigend aus. Es werden jedoch Formelemente, etwa ahnlich dem Durchschnitt 
der Platten von Malopterurus, mit runden Kernen und einfach buchend, nach- 
gewissen. Andererseits finden sich gewaltige Mengen dicker markhaltiger Nerven- 
fasern mit reichen biischelférmigen Verzweigungen. Der Zusammenhang der 
(etwaigen) beiden Elemente aufzukliren gelingt aber nicht in befriedigender 
Weise.” 
This is accompanied by a figure which is reproduced in Plate XIX, Fig. 24. 
Fritsch, after a careful examination of specimens of this species, doubts the existence 
of these elements. The region marked “‘a’’ by Sachs was occupied, in the speci- 
mens I examined, by connective tissue fibers and the edge of the two lateralis 
muscles. Higenmannia virescens is the only other Gymnotid besides E. electricus to 
which electric tissue has been ascribed. 
