STICKLEBACKS. 123 
himself beneath, does his best to drive in his 
spear, if the other be not quick enough to dart 
upwards and escape the thrust; thus squaring 
they fight round after round until the death or 
flight of one ends the combat. 
I have often, when tired, lain down on the bank 
of a stream, beneath the friendly shade of some 
leafy tree, and gazing into its depths watched the 
sticklebacks either guarding their nests already 
built, or busy in their construction. The site is 
generally amongst the stems of aquatic plants, 
where the water always flows, but not too swiftly. 
He first begins by carrying small bits of green 
material, which he nips off the stalks, and tugs 
from out the bottom and sides of the banks ; these 
he attaches by some glutinous material, that he 
clearly has the power of secreting, to the different 
stems destined as pillars for his building. Dur- 
ing this operation he swims against. the work 
already done, splashes about, and seems to test 
its durability and strength; rubs himself, against 
the tiny kind of platform, scrapes the slimy: 
mucus from his sides, to mix with and act 
as mortar for his vegetable bricks. Then he 
thrusts his nose into the sand at the bottom, 
and bringing a mouthful scatters it over the 
foundation; this is repeated until enough has 
