COLORS OF THE DEEP-SEA CRUSTACEA. 255 



blue,* but on the second segment it is parti-colored, — blue and light yellow. 

 The two colors in the latter case are not disposed in accordance with the 

 bilateral symmetry of the prawn, but the division between them forms a 

 diagonal line across the middle of the segment, and results in a most abnor- 

 mal color pattern. 



The change of Pouchet's prawns, nnder the influence of light, from red, 

 through blue, to light yellow, suggests the thought that the unique color- 

 ation of the deep-sea prawn figured on Plate H may be due to a change of 

 color undergone by the animal as it was brought up into the full blaze 

 of day. Such an interpretation is the more plausible, since the coloration 

 shown in this specimen does not appear to be a specific chai-acter. Although 

 upwards of 140 specimens of Bentliesic//mus tanneri had been collected through 

 tlie whole course of the voyage, from a date as early as February 24, yet this 

 peculiar pattern in blue and yellow was not observed until April 22, the last 

 day of the cruise. 



Viewed in this way, the blue is a transient tint assumed by the abdomi- 

 nal spots during their passage from a deep red, such as is still retained by the 

 anterior one of the series, to the pale yellow which already pervades a con- 

 siderable part of the second and begins to tinge the border of the third. 

 This supposition, implying, as it does, the persistence of the cyanic pigments 

 in the red, deep-sea Crustacea, accords well with the fact already noticed, that 

 the eggs of these creatures are often brilliant blue. 



* The blue color is much too lieht iu the fisrure. 



