I9I7-] S. Kemp: Fauna of the Matlah River. 241 



and is perhaps the nearest approach to the deep-sea oozes that is 

 to be found in shallow water. 



A diminished supply of light, low visibility and the very soft 

 nature of the bottom appear to me to have been the principal 

 factors that have determined the character of the Matlah fauna. 

 The colour phenomena seem for the most part to be controlled 

 by the first two of these factors. The presence of red pigmenta- 

 tion in deep-sea Crustacea is probably brought about in some 

 way not yet fully understood in response to a diminished supply 

 of light and, if this is so, there is every reason to think that the 

 red colouration so commonly met with in the Matlah prawns is 

 precisely similar in origin. In these cases there is no evidence 

 that the colour has any protective significance. It is otherwise, 

 however, with the peculiar translucency of the tissues that ma}^ 

 exist either in combination with, or in absence of red pigment. 

 This feature is clearly of protective valua in the Matlah fauna ; 

 whether it is more than fortuitous in deep-sea forms we have 

 at present no means of ascertaining. 



The structural modifications, on the other hand, more particu- 

 larly the elongation and attenuation of fin-rays and appendages, 

 appear to be correlated with the nature of the bottom, and the 

 evidence afforded by the inhabitants of the Matlah River suggests 

 that this factor has had a greater influence than has generally 

 been supposed in moulding the character of many deep-sea species. 



