CHAPTER LV 

 ORDER OF HALF-GILLED FISHES 



HEMIBRANCHII 



BECAUSE of the fact that a few very small fishes have 

 less than their rightful number of gill-arches, and 

 shoulder-girdles with one bone only instead of two, the 

 Order of Half-Gilled Fishes has been created. 



THE STICKLEBACKS are very small fishes, only a few 

 inches in length, and derive their name from the formidable 

 dorsal spines that stand upon the back in front of the dorsal 

 fin. We have Two-Spined, Four-Spined, and Ten-Spined 

 Sticklebacks, all three being found in brackish water along 

 the Atlantic coast from Cape Ann to New Jersey. 



All the Sticklebacks are celebrated for their nest-building 

 habits. The abdomen of the male fish has been provided 

 with a large gland which is "filled with a clear secretion which 

 coagulates into threads" when it conies in contact with 

 water. At first the fluid is colorless, but after contact with 

 water it becomes whitish, and its many fibres hang together 

 like strings of spaghetti. (Ryder.) 



The entire work of nest-building is performed by the 

 male Stickleback. It begins by selecting a bottom situation, 

 in a gentle current, wherein the nest can be attached to two 



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