PAEENTAL CARE AMONG FRESH-WATER FISHES. 



459 



The electrical or electric catfish is the only generally recognized 

 species of the family, although several nominal species have been 

 proposed from time to time. Another name by which it is known is 

 raad, raa-ard, or raada. This name, by which it is generally known 

 to the Arab fishermen of Egypt, means thunckn". and thus the natives 

 liave connected the fish with the phenomenon coincident with the 

 effect Avhich Europeans indicate in the name (electric catfish) which 

 they have given. Raad is an excellent name, and that will be used 

 here. 



The raad is indeed especially noteworthy on account of the remark- 

 a])le develo})ment of the electrical apparatus and function. An indi- 

 vidual no longer than a hand's length can give quite a disagreeable 

 shock, as the present Avriter can testify from personal experience. 

 " Both the director and some of the keepers, having received strong 

 electrical shocks from comparatively small '" fishes in the aquaria of 

 the Egyptian Zoological Gardens, cared not " to experience how 

 powerful a shock the large fish could give." 



Fig. 37. — liaad or electric catfish (Malaptcriiriis clcctricus\. After Boulengcr. 



In the words of Fritsch (181);>), the raad or Malapterurus belongs 

 " to quite a different category from other electric fishes." "A trans- 

 verse section of the Avhole fish shows the difference at once. The body 

 of the animal is enveloped in a very thick electric skin, constituting 

 one electric organ. Muscular tissue is nowhere deficient, other histo- 

 logical elements must therefore have furnished the material for the 

 electric ])lates, which are packed very close in the lozenge-shaped com- 

 })artments of the skin." 



In more detail, Francis (jotch (in 1801)) explained the structure of 

 tlie electrical organ: 



It is situated in the sldii enelosiiiij tlie wliole body of the fish, and has a beau- 

 tiful and eliaracteristic appearance wlien seen in niieroseopie sections. Each 

 organ consists of rows of conipartnients, and each compartment has shni^ 

 atliwart it a peculiar i>rotoi)lasmic disc shaped like a peltate leaf, with a project- 

 ing stalk on its caudal side. Nerves enter each compartment, and end, according 

 to the recent work of Ballowitz, in the stalk of each disc. I'.y these nerves 

 nervous impulses can reach the organ; the arrival of such imimlses at the 

 nerve terminations evokes a state of activity which is associated with the devel- 

 opment of electromotive charges of considerable intensity constituting the organ 

 shock. The shock is an intense current traversing the whole organ from head to 



