SEA-HORSE AND PIPE-FISH 



^77 



in sharp-edged rectangles, whose corners became produced 

 as spines. At this stage of evolution its appearance might 

 well be represented by (Fig. 185 A) 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 prcJiensile, — 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. As a probable de- 

 velopment of prehensilism, three 

 changes may next have been 

 wrought : the flexure of the neck 

 region, the thickening of the 

 trunk, and the metamorphosis 

 of the fins. The first change 

 may have been brought about 

 by the normal position of the 

 fish's axis becoming, as is well 

 known, vertical ; the head then 

 assumes its normal horizontal 

 plane and thus parallels mildly 

 the cranial flexure of higher ani- 

 mals. The enlaro^ement of the 



° Fig. 185. — The sea-horse, /^z^- 



trunk region is evidently of static pocampus heptagottus, Raf. x \. 



, r^, ,^ ^. r . 1 (After GooDE in U. S. F. C.) East 



value. The alteration of the pO- coast of North America. 



sition, size, and degree of move- 

 ment of the pectoral fins, the loss of the ventrals and the 

 changed function, now one of propulsion, of the dorsal, 

 appear clearly the result of the altered plane of the fish's 

 motion. Further structural changes might with interest 



N 



