THE WONDERS OF THE SHORE. 131 
different type; as indeed are those seemingly iden- 
tical gills, if you come to examine them under the 
microscope, having to oxygenate fluids of a very dif- 
ferent and more complicated kind; and, moreover, 
the Cucumaria’s gills were put round his mouth, 
the Doris’s feathers round the other extremity ; that 
grey Eolis’s, again, are simple clubs, scattered over 
his whole back, and in each of his nudibranch 
congeners these same gills take some new and 
fantastic form; in Melibea those clubs are covered 
with warts; in Scyllea, with tufted bouquets ; in 
the beautiful Antiopa they are transparent bags; 
and in many other English species they take every 
conceivable form of leaf, tree, flower, and branch, 
bedecked with every colour of the rainbow, as you 
may see them depicted in Messrs. Alder and Han- 
eock’s unrivalled Monograph on the Nudibranch 
Mollusca. 
And now, worshipper of final causes and the mere 
useful in nature, answer but one question—Why 
this prodigal variety? All these Nudibranchs live 
in much the same way: why would not the same 
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