278 THE ANGLER-NATURALIST. 



the stomach (fig. 2) . At this ' ' bag-stage " of its develop- 

 ment, the half-formed fry is exceedingly delicate, the dis- 

 placement of a stone, or the slightest bruise or injury, 

 proving instantly fatal. Its appearance is also very curious. 

 The future monarch of the stream is represented by .a 

 mere ragged line, fringed at the edges and almost trans- 

 parent, the head and eyes being prominent and altogether 

 out of proportion to the body, which measures only about 

 f ths of an inch in length, and is of a pale peach-blossom 

 or azure tint. An examination of one of these newly- 

 hatched creatures through a powerful microscope exhibits 

 in perfection the system of the double circulation*, or 

 passage and repassage of the blood-globules through the 

 veins and arteries a fearful and wonderful sight, which 

 seems to bring the beholder face to face with the great 

 mystery of life, in at least its visible aspect. 



In thirty-five or forty days from the time of hatch- 

 ing, the yolk-bag disappears, and the fry becomes a perfect 

 little fish of about an inch long (fig. 3), with the fins sepa- 

 rated and properly developed, and the tail deeply forked at 

 the end. The general colour now also changes to a light 



* The gills of fish represent the lungs of warm-blooded animals. 

 The blood, however, after being forced to the gills by the heart, does 

 not, as in the latter class, flow back again to the heart, to be thence 

 propelled throughout the body, but proceeds direct to the arteries lying 

 under the spine, and continues its course to the tail, gradually filtering 

 its way back to the heart, and thence to the gills, and so on in a con- 

 tinuous circle. By this arrangement the fish is enabled to exist upon 

 the comparatively small amount of oxygen contained in the water in 

 other words, becomes "cold-blooded." 



