EXPLANATION OF PLATES 



The photographs, with the exception of le (by Dr. Victor Bauer), were all taken 

 by the author. The water-color sketches (plate 6) are the work of Mr. V. Serino, 

 an artist in the employ of the Naples Station. 



The figures all relate to a single species, Rhomboidichthys podas (Delaroche), 

 and all are reduced to approximately one half the natural size. 



Figures bearing the same number represent different views of the same fish. 

 These are arranged with a view to easy comparison. Thus the order in which the 

 views of a single specimen are presented does not necessarily bear any relation to 

 the order in which the corresponding changes were undergone in the course of the 

 experiments. 



For an account of the photographic methods employed see pp. 418-421 of the text. 



PLATE 1 



EXPLANATION OF FIGURES 



Views of specimen no. 1 : a, on a dark, mixed sand (after one day) ; b, on fine 

 gravel (after one day); c, on fine jet-black (magnetite) sand (after four days); 

 d, on a very coarse reddish sand (after eight days); e, on a coarse gravel, devoid of 

 sand (after two days). 



