ric fishes, the current proceeds from the head to the tail.

The electric cat-fish, which grows to a length of 3 ft. in the Congo,
has a wide distribution in Africa, extending from the Nile to the
Zambezi and from the Senegal to the Congo. It was well known to the
ancient Egyptians, who have depicted it in their mural paintings and
elsewhere, and an account of its electric properties was given by an
Arab physician of the 12th century; then as now the fish was known under
the suggestive name of _Raad_ or _Raash_, which means "thunder."

Gunther's _Siluridae Branchicolae_ comprise the smallest and least
developed members of the family; they are referred to two genera only
from South America, _Stegophilus_ and _Vandellia_, the smallest of which
does not exceed the length of 2 in. Their body is soft, narrow,
cylindrical and elongate; the dorsal and anal fins short; the vent far
behind the middle of the length of the body; gill-membranes confluent
with the skin of the isthmus. Each maxillary is provided with a small
barbel; and the gill-covers are armed with short stiff spines. Their
small size notwithstanding, these Silurids are well known to the
Brazilians, who accuse them of entering and ascending the urethra of
persons while bathing, causing inflammation and sometimes death. Some
certainly live parasitically in the gill-cavity of large Silurids, and
F. Silvestri has observed _Stegophilus insidiosus_ to suck the blood in
the gills of _Platystoma coruscans_, a Silurid growing to a length of 6
ft.

[Illustration: FIG. 4.--_Callichthys armatus_, from the upper Amazons.]

The mailed cat-fish of the South American genus _Callichthys_ builds
regular nests of grass on leaves, sometimes placed in a hole scooped out
in the bank, in which they cover their eggs and defend them, male and
female sharing in this parental duty. In the allied _Corydoras_ a
lengthy courtship takes place, followed by an embrace, during which the
female receives the seminal fluid in a sort of pouch formed by the
folded membranes of her ventral fins; immediately after, five or six
eggs are produced and received in the pouch, to be afterwards carefully
placed in a secluded spot. This operation is repeated many times, until
the total number of eggs, about 250, have been deposited. In accordance
with these pairing habits, the pectoral spines of the male, which are
used in amplexation, are larger and stronger than those of the female.
These fish are monogamou