176 THE HARMONIES OF NATUKE. 



lead the vagrant life of the juvenile oyster or adolescent 

 sponge, bounding nimbly along by the simultaneous stroke of 

 their numerous legs, and possessed of open eyes to pilot their 

 course through the waters ; but, when once fixed, they remain 

 attached for the remainder of their lives, and then their struc- 

 ture undergoes a most remarkable change. The shell is gradually, 

 formed, the eyes are cast away as being no longer needed, and the 

 now useless feet are converted into extremely useful arms or cirri, 

 resembling a plume of purple feathers. 

 These cirri are constantly in motion 

 as long as they are bathed in water, 

 projecting outwards, and expanding into 

 an oval concave net then retracting 



A part of one of the arms 



considerably magnified. inwards, and closing upon whatever 

 may have come within their reach. They are so judiciously 

 placed that any small matter which becomes entangled within 

 them can rarely escape, and finds a ready passage to the mouth. 

 The currents produced in the water by their perpetual motion serve 

 also to aerate the blood, so that these delicate organs act both as 

 gills and as prehensile arms. In spite of their sessile condition, 

 the Cirripeds, as these curious animals are named, have not 

 been left without protection against hostile attacks ; for at the 

 approach of danger they shrink within their shell, and close its 

 orifice against a host of hungry intruders. Living above low- 

 water-mark, the Acorn-shells are necessarily exposed to the air 

 for several hours during the recess of every tide a proof of their 

 power to resist ungenial circumstances, and of the beautiful har- 

 mony of their organisation with the mode of life which has been 

 marked out for them in the plan of Creation. 



While the Cirripeds grasp, as in a living net, any minute 

 creatures that may be roving withing their reach, the Siphono- 

 stomata (Fish-lice, lernese) lead a parasitic life chiefly upon 

 fishes, sucking their juices with a bloodthirsty proboscis. The 

 fish-lice wander about freely on the body of their victims, as 

 grazing animals on their pasture-grounds ; while the Lerneas, 

 after having, like the- barnacles, led a vagrant life in their first 

 youth, remain ever after clinging to the spot on which they once 

 have settled. 



Both are blind, and have but an indistinct head ; while the 



