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 Centrarchidae. 



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 •. . Scisenidae. 



Suborder Loricati. 



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



Family GASTEROSTEIDiE 



(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; preinaxillaries protractile; maxillary bent at 

 right angles and overlapping premaxillary at corner of mouth; teeth 

 sharp, in a narrow band on each jaw; no teeth on vomer or palatines; 

 pyloric cseca 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 very 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, clogging 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 by silk-like threads formed 

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

 substance* secreted by this gland, which is in reality the kidney, is 



*See Mobius, Arch. f. Mikr. Anat., Vol. 25, p. 554. 



