BREEDING HABITS OF THE YELLOW CAT-FISH. 
153 
a pale yellow color. The number of eggs deposited was estimated at 2,000. The 
incubatory period was 5 days in a mean water temperature of 77 F. , the lowest 
temperature being 75° and the highest 80°. About 12 hours intervened between the 
hatching of the first and last eggs. Active movement was observed in the embryos 
40 hours after the eggs were laid. Fully 99 per cent of the eggs hatched into normal 
fry, a few weak and deformed fry and a few unfertilized or dead eggs being noticed. 
Growth of young . — When the fry first emerged from the egg they were about 
one-quarter of an inch in length, and of a yellowish, transparent color. By the sec- 
ond day the skin of the back had begun to darken, and by the end of the fourth day 
the entire upper parts were uniformly bluish black and the under side had become 
whitish. On the third day the barbels at the angles of the mouth and the pectoral 
and dorsal spines were clearly visible through the glass front of the aquarium. 
Until 6 days old they remained on the bottom in densely packed, wriggling 
masses, the largest lot in the nest and several smaller lots in other parts of the 
aquarium. On the sixth day they began to rise vertically a few inches above the 
bottom, at first falling back at once, but gradually remaining longer above the bot- 
tom. By the end of the seventh day they were swimming actively, and practically 
all collected in a school just beneath the surface, where they remained for two days. 
They then began to scatter, and subsequently did not school. 
The relatively large yolk-sac had nearly disappeared by the sixth day, when 
they began to eat finely ground beef liver, and they were feeding ravenously by the 
eighth day. Between feeding times, they passed much of the time on the bottom of 
the aquarium in search of food, which they ate in an almost vertical position, head 
downward; they also browsed on the sunny side of the aquarium, where there Avas 
a short growth of algae. The early growth Avas rapid, but not uniform; on the 
eleventh day their length varied from one-half to three-fourths of an inch. At the 
age of 2 months the average length was 2 inches; but after that time the growth was 
very slight, and in January, 1903, six months after hatching, the length of the sur- 
vivors was only 2| to 2^ inches. The slow growth Avas undoubtedly due to the fact 
that the fry Avere retained in small troughs where the conditions were unnatural. 
Care of eggs and young . — During the entire hatching period both parents were 
incessant in their efforts to prevent the smothering of the eggs, to keep them clean, 
and to guard against intruders. The eggs were kept constantly agitated and aerated 
by a gentle fanning motion of the lower fins, and foreign particles, either on the 
bottom of the nest or floating near the eggs, were removed in the mouth or by the 
fins. The most striking act in the care of the eggs was the sucking of the egg masses 
into the mouth and the blowing of them out, this being repeated several times Avith 
each cluster before another lot was treated. 
The male was particularly active in watching for intruders, and savagely attacked 
the hands of the attendant who brought food, and also rushed at sticks or other 
objects introduced into the aquarium. Practically the entire work of defense was 
assumed by the male, although the female occasionally participated. 
During the time the fry were on the bottom the attentions of the parents were 
unrelaxed, and, in fact, were increased, for the tendency of the different lots to become 
scattered had to be corrected, and the dense packing of the young in the corners 
seemed to occasion much concern. The masses of fry were constantly stirred as the 
eggs had been by a flirt of the tins, which often sent dozens of them 3 or 4 inches 
upward, to fall back on the pile. 
