GASTEROSTEID^ — THE STICKLEBACKS 221 



g. Anal spines 3 to 10. 



h. Lateral line wanting Elassomidae. 



hh. Lateral line present. 

 i. Dorsal fins confluent, the spinous portion low or high; in forms with the 

 notch deep, approaching separation, the highest dorsal spine is but little 



more than % height of the highest ray Centrarchidse. 



ii. Dorsal fins either (1) separate and with soft and spinous portions about 

 equally high, or (2) barely confluent, with the notch very deep and with 

 the highest dorsal spine as high or higher than the highest soft ray (which 



definition does not include marine genera) Serranidae. 



gg. Anal spines 1 or 2, never more than 2. 



h. Lateral line not extending on rays of caudal fin Percidae. 



hh. Lateral line extending on rays of caudal fin Sciaenidse. 



Suborder Loricati. 



ff. Body naked, or variously armed with prickles or bony plates Cottidae. 



Family GASTEROSTEIDiZE 



THE STICKLEBACKS 



Body more or less fusiform, somewhat compressed, tapering behind to a 

 slender caudal peduncle; skin naked or with vertically oblong bony plates; no 

 true scales; skeleton osseous; four anterior vertebrae more or less enlarged; 

 middle and sides of belly shielded by the pubic bones; ventral fins abdominal 

 or subabdominal, consisting of a stout spine and one or two rudimentary rays; 

 dorsal fin preceded by 2 or more free spines; caudal lunate; no mesocoracoid; 

 gill-membranes broadly joined, free from isthmus or not free; branchiostegals 

 3; gill-rakers moderate or rather long; mouth-cleft oblique; premaxillaries 

 protractile ; maxillary bent at r ght angles and overlapping premaxillary at 

 corner of mouth; teeth sharp, in a narrow band on each jaw; no teeth on 

 vomer or palatines; pyloric caeca present, few in number; air-bladder simple. 



These are small fishes, inhabiting fresh waters and arms of 

 the sea in northern Europe and America. Genera 5, species 

 about 12; two species, representing two genera, found in Illinois. 



The fresh-water sticklebacks are ver}^ similar in their habits. 

 All are active, pugnacious, and greedy, and, in spite of their 

 small size, they are known to be very destructive to the fry of 

 other fishes. In certain localities along the Atlantic coast they' 

 occur so abundantly as to be a nuisance to the fishermen, clog- 

 ging the nets used for smelt. Certain European species will 

 bear with impunity transplantation from fresh water into salt 

 water, and vice versa. 



Most or all of the sticklebacks build nests, constructing 

 them out of sticks which they fasten together b}^ silk-like threads 

 formed from the secretion of a gland, found only in the males. 

 The substance* secreted by this gland, which is in realit}' the 



* See IMobius Arch. f. "SWkr. Anat. Vol. 2.5 p. 554. 



