PARENTAL CARE AMONG FRESH- WATER FISHES. 411 



been, developed into a habit. Those and other provisions for the 

 care of the eggs do not make excessive demands on our receptive 

 capacity or imagination. It is only when we consider the ca^e of tlie 

 sticklebacks that tlie combination of ai)titudes for nest making im- 

 presses ns. In them complexity is carried to an extreme. There is 

 a sympathetic development of the kidneys and the testes; there is the 

 synchronous response of both to external stinudi; tliere is the reaction 

 of both on the brain and of the brain to external conditions; there 

 is the elaboration of the wonderful thread which is used lo bind the 

 nest materials; there is the instinct to use the thread; there are, 

 finally, the regular aptitudes and impulses which are shared Avith the 

 majorit}' of fishes. Such an accunndation and convergence of struc- 

 tural, physiological, and psychological characters almost force upon 

 us a rejection, as explanation, of natural selection or sexual selection. 

 The development manifested in the Gasterosteids is, indeed, one of 

 the greatest wonders of the evolution of animal life. Nevertheless, 

 it may not seem so extraordinary if we extend our researches beyond 

 the class to which they belong. 



Naturally tlie elal)oration for the perpetuation of the species in the 

 Gasterosteids is unique in the class of fishes, but there is to some 

 extent an analogous provision, although not so complicated, for the 

 animal economy in certain other classes, as in the case of the Avebs 

 of most spiders and the cocoons of some insects, as notably the silk- 

 worms. ]Mollusks and Annelida furnish other illustrations. Of 

 course in those cases the analogous secretions are not produced by 

 liDmologous organs, but by very different ones, very different from 

 each other as well as from those of the sticklebacks. 



As this article is intended to summarize existing knowledge re- 

 specting the breeding habits of some of the fishes in question, the 

 original words in which the facts are recorded are given in most 

 cases — in fact, whereA'er it could be don'e without interference with the 

 mode of treatment or sequence adopted for the narration. The text, 

 hoAvever, is by no means confined to information respecting the nests 

 and breeding habits. Most of the species are little knowm or even (piite 

 unknown to many persons and yet are very interesting for other 

 reasons than their parental instincts. Consequently quite detailed 

 accounts of their habits in general as Avell as their places in nature 

 are added. The illustrations are mostly borrowed and are derived 

 from various sources, as will be indicated in connection with the 

 respective figures. Among the original illustrations are those of a 

 fish longest known — the Glanis of the ancient Greeks, never before 

 figured. 



