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 {Protopterns) 

 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 (Rhodeus 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 



