THE ORDERS OF TELEOSTOMOUS FISHES 495 



following characters as common to both groups: (i) the parapo- 

 physes are developed on all the abdominal vertebrae; (2) the 

 supraclavicle when present is small; (3) the exoccipitals are not 

 united above the basioccipital ; (4) the supraclavicle, when 

 present is reduced in size;. (5) Fistularia and Aulostomus have 

 processes running backward from the epiotics, which are strikingly- 

 similar to the epiotic processes possessed by all the Percesoces. 

 On the other hand, the Hemibranchs easily stand apart from the 

 Percesoces "in having no opisthotics and usually no parietals; 

 in having the posttemporals simple, not typically forked; and 

 in having the clavicle composed of a single piece when present 

 (composed of two pieces in the Percesoces). " 



The most generalized form, Gasterosteus, is carnivorous and 

 active, but the prey is the small "fry" of other fishes which 

 the Sticklebacks seek out "with the utmost industry, sagacity, 

 and greediness." The taste for minute prey to be sought by 

 poking about in odd corners may have determined some of the 

 peculiar specializations of the Sea-horse order. We may imagine 

 these to have continually sought smaller and smaller food until 

 the tiny particles came to be sucked up by the elongate muzzle. 

 After probably passing through a stage somewhat like Syngnathus 

 but less eel-like the ancestral Sea-horse did not need the quick- 

 darting form of body to capture its food or escape enemies ; hence 

 the fan -like tail fin was suppressed (in Hippocampus) , and the 

 rapidly vibrating pectoral and dorsal fins enabled the fish to 

 poise, humming-bird fashion, while sucking food through its tub- 

 ular beak. The pectoral fins have been thought also to assist in 

 drawing a steady current of water through the gill chamber. At a 

 a very early period protection was secured by the development of 

 an osseous cuirass and (in certain forms) of fucus-like outgrowths 

 of the skin. Respiratory improvements consisted in the elabora- 

 tion of tufted gills from the pectinate type. For the elaborate 

 nesting habits and attentive care of the eggs by both sexes in 

 the Sticklebacks, may have been substituted first the adhesion 

 of the eggs to the abdomen of the male, then the develop- 

 ment in the male of abdominal grooves and ridges to hold 

 the eggs, finally, by fusion of opposite ridges, a perfected 

 pouch. 



