244 
ANIMAL INTELLIGENCE. 
away to a safe distance ; then, after patting down the nest, he 
proceeds in search of another female. The nest is built and the 
ova deposited in about twenty-four hours. The male continued 
to watch it day and night, and during the light hours he also 
continually added to the nest. 
The marine fifteen-spined sticMehsick(Gasterosteus spinachia) 
affords another instance of nest-constructing fishes. The places 
selected for their nests are usually harbours, or some sheltered 
spots to where pure sea water reaches. The fish either find 
growing, or even collect some of the softer kinds of green or red 
seaweed, and join them with so much of the coralline tufts 
( Janice ) growing on the rock as will serve the purpose of afford- 
ing firmness to the structure, and constitute a pear-shaped mass 
five or six inches long, and about as stout as a man’s fist. A 
thread, which is elastic and resembles silk, is employed for the 
purpose of binding the materials together : under a magnifier 
it appears to consist of several strands connected by a gluey 
substance, which hardens by exposure to the water. 1 
M. Carbonnier, who has studied the habits of the Chinese 
butter fly- tish ( Macropodus ) in his private aquarium in Paris, 
where he had some in confinement, observed that the male 
constructs a nest of froth of considerable size, 15 to 18 centi- 
metres horizontal diameter, and 10 to 12 high. He prepares 
the bubbles in the air (which he sucks in and then expels), 
strengthening them with mucous matter from his mouth, and 
brings them into the nest. Sometimes the buccal secretion 
will fail him, whereupon he goes to the bottom in search of 
confervae, which he sucks and bites for a little in order to stimu- 
late the act of secretion. The nest prepared, the female is in- 
duced to enter. Not less curious is the way in which the male 
brings the eggs from the bottom into the nest. He appears 
unable to carry them up in his mouth ; instead of this, he first 
swallows an abundant supply of air, then descending, he places 
himself beneath the eggs, and suddenly, by a violent contraction 
of the muscles in the interior of his mouth and pharynx, he ex- 
hales the air which he had accumulated by the gills. This 
air, finely divided by the lamellae and fringes of the gills, 
escapes in the form of two jets of veritable gaseous powder, 
which envelopes the eggs and raises them to the surface. In 
this manoeuvre the Macropodus entirely disappeared in a kind 
of air-mist, and when this had dissipated he reappeared with a 
1 Quoted from Francis Lay, F.L.P., ‘ Instincts and Emotions of Fish, 
Journ. Linn. Soc ., voi. xv., pp. 36-7, where see for other cases of nest' 
building among fish. 
