PISCESSUB-CLASSin.—TELEOSTOMI. 



formed by a fold of skin arising on each side, and the two meeting in the 

 middle line. The manner in which the eggs are conveyed into this pouch 

 appears to be unknown, but when once there they are completely enclosed by 

 the junction of the edges of the two folds of skin, and thus remain till they 

 are hatched into minute eel-like pipe-fish, which soon make their way into 

 the water by bursting open the folds of the pouch. In the sea-horses the 

 development is carried one stage further, the nursing-pouch being closed 

 along the middle line, so as to communicate with the exterior only by means 

 of a small aperture at the anterior end, through which the eggs are by some 

 means or other introduced, and by which in due course the young make then- 

 escape. Certain pipe-fishes (Doryichthys) differ from the ordinary forms in 

 that the males have the pouch placed beneath the abdomen instead of under 

 the tail ; and it is remarkable that in some allied genera {Nerophis) the eggs 

 are simply attached to the lower surface of the abdomen of the male without 

 the development of any pouch. 



Both the Solenostomatidce and Syngiiathidw are feeble swimmers ; they 

 generally frequent coasts well protected by sea-weed, to which the species 

 provided with prehensile tails attach themselves by means of that useful 

 appendage. In swimming, they generally maintain themselves in a more or 

 less nearly vertical position. Writing of the sea-horse. Dr. Bashford Dean 

 says that, " in spite of its many structural oddities, its genetic kinship with 

 the stickle-backs cannot be doubted. Yet to have attained its present form, 

 its evolution must have carried it along a widely divergent path. It may, in 

 the first place, have fused the lines of its metameral scales, di-\-iding off the 

 surface of its elongate body in sharp-edged rectangles, whose corners have 

 become produced into spines. At this state of evolution its appearance 

 might well be represented by that of the kindred pipe-fish. To secure more 

 perfect anchorage in its algous feeding-ground, its body-terminal must now 

 have discarded its fin-membranes and become prehensile, probably the most 

 remarkable adaptation in the entire class of fishes, since it causes metameral 

 organs to change the plane in which they function from a horizontal to a 

 vertical one." 



SUB-ORDER III. — PLECTOGUATHI. 



The spine-clad globe-fishes, of which dried specimens are so frequently 

 exhibited in old curiosity shops, may be taken as a familiar example of this 

 small sub-order, which, like the last, includes highly modified and specialised 

 forms. All these fislies have a narrow mouth, and some of the bones of the 

 upper jaw fused together, while in some of them the jaws are produced into 

 a beak-like form. They have but few segments in the back-bone, and 

 whereas the bones of the head are fully hardened, those of the rest of the 

 skeleton are comparatively soft. In form, the gills are pectinate ; the gill- 

 apertures being very small, and placed in advance of the pectoral pair of fins. 

 If the pelvic fins persist they are reduced to more spines ; the spinous dorsal, 

 too, is more or less rudimental, although the soft dorsal is generally well 

 developed and situated far back, immediately over the anal. Very various 

 is the covering of the body, the skin in some forms being naked, while in 

 others it is dotted over with long spines ; in others the whole head and body 

 is invested in a complete cuirass of true bone, while in others there are 

 roughened scales. All, however, agree in the absence of a duct to the 

 air-bladdex'. 



