PARENTAL CARE AMONG FRESH-WATER FISHES. 407 



embryos leave, after which the skin returns to its former condition. 

 The only analogue to this occurs in certain anurous batrachians, but 

 in such in a less specialized condition and on the back. 



The most specialized of all the care takers are the sticklebacks, or 

 Gasterosteids. These have an important organ (the kidney and its 

 adjuncts) especially modified histologically to yield a thread analo- 

 gous to that developed by spiders and used for binding the objects 

 selected for a nest. So far as known none of the related fishes has 

 the same structural peculiarity, but it is quite possible, if not prob- 

 able, that their nearest relatives of the North Pacific — the Aulo- 

 rhynchids — may have a similar history. It is scarcely within the 

 range of possibility that an analogous structure like this should have 

 been independently developed a second time in unrelated fishes. 



One remarkable, and to some astonishing, fact is the want of corre- 

 lation that may sometimes exist within a natural family betAveen 

 structural features and habits. This is strikingly manifest in the 

 typical catfishes or Sihirids. Neither of the parents of the well- 

 known wels of central and western Europe appears to care for eggs 

 or young, but the male of its near relation of Macedonia^the 

 gianis — assumes a special charge of his consort's labor. Opposite 

 ways of making their nests are practiced by the North American cat- 

 fishes on one hand and certain Australian ones on the other. PjU- 

 largement of the eggs is manifested in another group and is associated 

 with their reception and carriage by the male in his mouth. 



In the last English work on fishes, the Cambridge Natural His- 

 tory ,° it is declared that, " with the exception of the pelagic Anten- 

 narhis^ which builds its nest in the sargasso weed in mid-ocean, 

 nest building and parental solicitude for the young are confined to 

 fresh water fishes and to marine forms with demersal eggs. Pelagic 

 ova must necessarily be beyond the scope of parental care." The 

 so-called Antennarivs is no exception; the species meant is not a 

 true AntennariifS, but belongs to a distinct though related genus — - 

 Pterophryne. Its history is a truly remarkable one and it has been 

 more widely noticed as a nest-building fish than any other except 

 the Gaxterosteids. In truth, lunvever, it does not build a nest at all. 

 The whole story is the result of a misidentification of the eggs of a 

 fish. In 1872, the celebrated naturalist. Prof. Louis Agassiz, attrib- 

 uted egg-bearing masses of gulf weed (sargassum), which he found 

 in the gulf stream, to the PteropJiryne which was abundantly asso- 

 ciated with them. His equally able son. Dr. Alexander Agassiz, 

 a decade later (1882), made known the remarkable egg raft Avhich 

 floated the eggs of a relative of the Pterophryne — the angler 

 {Lophius piscatorius) . This discovery may have led to thought, but 



o Cambridge Natural History, Vol. VII, p. 414 (1904), 



