DESCRIPTION OF PLATES XXVII. to XXXVIII. 



The figures on Plate XXVII. are reproduced from photographs made by the Author ; the rest of the 

 figures are reproductions of drawings made by the Author with the Abbe drawing apparatus. All the 

 figures are reduced from these drawings, most of them to two-fifths of the size of the originals ; the 

 final magnification is marked on each figure. 



The letters on the Spicule drawings correspond with those used in the text to indicate the diiferent 

 sorts of spicules. 



N.B. — Hair spicules, which occur in many of the sponges, are not shown in the figures. 



The significance of the letters on the other drawings is given in the following list : — 



LIST OF FIGURES. 



