154 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The very young 1 fry were also taken into the mouths of the parents and blown 
out, especially those which became separated from the main lot and were found in 
the sand and sediment. The old fish would take in a mouthful of fry and foreign 
particles, retain them for a moment, and expel them with some force. After the 
young began to swim and became scattered, the parents continued to suck them in 
and mouth them, and, as subsequently developed, did not always blow them out. 
An interesting habit of the parents, more especially the male, observed during 
the first few days after hatching was the mixing and stirring of the masses of young 
by means of the barbels. With their chin on the bottom, the old fish approached the 
corners where the fry were banked, and with the barbels all directed forward and 
Hexed where they touched the bottom, thoroughly agitated the mass of fry, bringing 
the deepest individuals to the surface. This act was usually repeated several times 
in quick succession. The care of the young may lie said to have ceased when they 
began to swim freely, although both parents continued to show solicitude when the 
attendant approached the aquarium from the rear. 
When 12 days old, about 1,500 of the fry were removed from the aquarium 
to relieve crowding, and placed in a hatching-trough such as is employed for salmon 
and trout. For some unknown cause, about 1,000 of these died during the first three 
days. The others survived with little or no loss, and are still on hand. 
The fry which were left with their parents continued healthy, but their number 
steadily decreased. There being no way for them to escape, and a closely woven wire 
screen preventing inroads from the exterior, it was suspected that the old fish were eat- 
ing their young, though they were liberally fed at suitable intervals. They were kept 
under close observation during the day, and were seen to be fond of mouthing the 
fry, more especially the weaker ones — a habit which at this stage seemed unnecessary. 
They were frequently seen to follow leisurely a fry, suck it in their mouth, retain it 
for a while, and then expel it, sometimes only to capture it again. There was no 
active pursuit of the fry, and the tendency seemed to be to spit them out. In one or 
two instances, however, it appeared that fry taken into the mouth were not liberated, 
the feeding instinct becoming paramount to the parental instinct. After all the fry 
which had been left with their parents had disappeared- in about 6 weeks after 
hatching — 18 fry from the trough were placed in the aquarium one evening, and only 
2 of these had survived on the following morning. 
During the entire period covered by these observations liver and beef were fed 
regularly to the brood fishes, and at no time did their appetites fail. There was 
apparently no interference with deglutition, or closure of the oesophagus, such as 
has been observed in some other cat-fishes, as half-inch cubes of meat were readily 
ingested during the entire time the fish were under observation. 
External sexual characters of adults . — Besides the fullness of abdomen which the 
mass of eggs gives to the female, there was in both pairs of fish under consideration 
another external feature by which the sexes could be distinguished. This was the 
shape of the snout and interorbital region, which in the males were noticeably flatter 
and broader than in the females. The males in both these cases were about 12 inches 
long and were an inch longer than their partners. 
