SOME STRANGE NURSING HABITS 349 
able size, I am not aware that any others have special 
arrangements for carrying about their eggs after extrusion, 
with the exception of the aberrant lung-fish (Protopierus) 
of tropical Africa, In this genus the numerous eggs and 
embryos are reported to be nursed in a long gelatinous 
pouch attached to the sides of the back of one of the 
parents, although which of the two is charged with this 
office does not appear to be ascertained. Several kinds of 
fish are, however, in the habit of constructing nests for the 
reception of their eggs, while a few take advantage of other 
animals for their protection. For instance, the females 
of the small roach-like fishes of which the continental 
bitterling (Ahodeus amarus) is the only European example, 
have the oviduct periodically prolonged into a tube of 
considerable length, by means of which the eggs are 
introduced within the shells of living fresh-water bivalve 
molluscs, where they remain secure from foes until hatched. 
Among the nest-building species the most familiar are the 
bullheads (Cottus), sticklebacks (Gastrosteus), and lump- 
suckers (Cyclopterus), in all of which, as in the other 
instances, the nest is formed and guarded by the male 
fish. In the sea-stickleback the nest is a large structure 
composed of pendent seaweeds, tightly bound together into 
a pear-shaped mass by means of a silk-like thread. When 
the eggs are safely deposited within its interior, the male 
fish immediately mounts guard, and has been known to 
continue uninterruptedly at his post for upwards of three 
weeks, Should any damage happen to the nest, so that 
the precious eggs lie open to the attack of any predaceous 
wanderer, the janitor forthwith sets to work with the 
greatest energy to repair the damage, poking his nose into 
the structure, and rearranging the materials till all is made 
right. Nests are also made by the fresh-water species, and 
