418 FRANCIS B. SUMNER 



'Code des Couleurs' of Klincksieck and Valette (Paris, '08). 

 Differences of color (as distinguished from shade) played, however, 

 a minor part in my observations, partly because no very striking 

 changes of color occurred, partly because of the difficulty of repro- 

 ducing changes of this sort. 



Photography.^^ The camera used^*^ was mounted vertically upon 

 a frame made for the purpose, the jar containing the fish being 

 placed upon a horizontal platform below. With a few exceptions, 

 the bellows of the camera was always drawn out to the same point, 

 so that practically all of my photographs are in the same scale. 

 This is slightly over two-thirds (69 hundredths) of the natural 

 size. In the present reproductions, this has been reduced to 

 approximately one-half of the natural size. 



Fortunately Rhomboidichthys podas is ordinarily a quiet 

 fish and may generally be depended upon to remain still long 

 enough to allow of a satisfactory exposure being made. The time 

 required for this varied, depending upon the light, from a small 

 fraction of a second to one minute or more. The intensity of 

 sunlight, during an average spring day in Naples, varies enormously 

 from hour to hour, and even from minute to minute, a fact which 

 made it very difficult in many cases for me to estimate the proper 

 time required for the exposure. It would have been much better, 

 had it been practicable, if an artificial light of constant intensity 

 had been employed, and the conditions of exposure, development 

 and printing had been identical in all cases. Thus alone would the 

 different pictures have been strictly comparable. 



As is well known by anj^one at all familiar with photography, 

 quite different appearances may be given to the same object by 

 the use of varying technique. This is particularly true of the 

 relative values of light and shade. An object of intermediate 



^' I must confess to having had no experience with this sort of photography- 

 prior to the work in hand, a fact to which, I fear, some of my results bear abundant 

 witness. My profound thanks are due to Dr. Victor Bauer, of the station staff, 

 for much assistance and instruction. 



1® This camera^was one made by Curt Bentzien, Goerlitz, and the lens by Voigt- 

 lander and Son ('Major'). Lumiere and Son's 'Blue Label' plates were used, 

 commonly 9x12 cm. in size, though in some cases 13x18 cm. 



