No. 5 (192I) MADRAS AQUARIUM 85 



sea-perch, Liitianus jahiigarah (Tarn. Miisidiniiii) inhabiting this 

 tank. In the mornings it is very pale in colour, nearly white, 

 except for the fins which are rosy ; towards evening the colour of 

 the body deepens till it is a distinct dull or smoky red. This deep 

 red tint is also assumed during excitement or when disturbed or 

 teased by its tank companions. 



Both in tank No. 8 and in this one are usually specimens of a 

 pretty blue serranid sea-perch, Serranus flavocacndcus (Tarn. Utha 

 Kalavai). Those in tank No. 8 are the younger and the signifi- 

 cance of its scientific name " the yellow and blue Serranus " will 

 be understood if the blue fishes with yellow markings in tank No. 

 8 be studied in comparison with the entirely blue individual in this 

 tank. It will be noticed that the shape and other characteristics 

 of all are the same, except in regard to colour, and they are indeed 

 one and the same species. The youngest show the fins bright 

 yellow, with the upper jaw and the edge of the operculum also 

 similarly coloured. The medium-sized show a great reduction in 

 the parts coloured yellow, and in the fully adult the yellow is com- 

 pletely lost. It is seldom that colour changes are so strongly 

 associated with different ages as in this fish and by having the 

 three stages in adjoining tanks these changes are more readily 

 observable than if the fishes were all together. 



TANK No. 10. 



A family of fat Sca-pcrches (Tam. Kalavai) of the genus 

 Serranus occupy this tank. They are the oldest inhabitants of the 



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Fig. 18. — Indian Reck Cod {Serranus iiiididosus^ . X y,- 



aquarium; three have been here for II years and have become 

 very tame. They have their regular hours for sleep, and at sunset 



