SEA-HORSE AND PIPE-FISH 127. 
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-jish, 
To secure more perfect.anchorage in its algous feeding- 
ground, its body terminal must now have discarded its fin 
membranes and become frehensile, — 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 enlargement of the 
ie ; 5 Fig. 185.— The sea-horse, Hif- 
trunk region is evidently of static pocampus heptagonus, Raf. x }. 
value. The alteration of the po- (After Goope in U.S. F.C.) East 
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 
