XVI. ON THE OCCURRENCE OF IRIDOCYTES 

 IN THE LARVA OF MICROHYLA ORNATA, 



BOUL. 



By C. R. Narayan Rao, M.A., L.T., University of Mysore, 



Bangalore. 



(Plate XI). 



Introduction. 



There are some good observations recorded as regards the 

 colour of batrachian larvae in life, but in most cases the descriptions 

 refer to preserved specimens. Such descriptions must necessarily 

 differ, for the material sent to leading authorities for examination 

 generally arrives in a state in which the colour is somewhat differ- 

 ent from what occurs in living forms, the usual methods of preser- 

 vation, either in alcohol or formalin, greatly affecting the pig- 

 ments. Moreover, the colouration of specimens of the same species 

 of batrachian is not uniform as a rule, inasmuch as it depends in 

 a great measure on the character of the surroundings from which 

 they are taken and the conditions under which they live. For 

 example, if the olive green tadpoles of the genus Rana or Rhaco- 

 phorus should be transferred, from the green weeds amidst which 

 they live, to a more exposed area of another pond, they turn grey ; 

 and if the same larvae should be retransferred to a third pond 

 with a black clayey bottom, they become brown. Similarly 

 dearth or abundance of food will greatly influence the colour. 

 Starvation nearly causes the absorption of the yellow pigments 

 with the consequence that the melanin chromatophores show 

 through to some extent, the tadpole looking more or less darker. 

 On the other hand, generous feeding favours the deposit of more 

 than one kind of lipochrome pigment, and accordingly the larvae 

 appear beautiful with a variet}^ of colours. 



The tadpole of M. ornata has been described by Capt. S. Flower 

 (Proc. Zool. Soc. London, 1899, p. 902), and there is a short note 

 on the same subject by Mr. H. S. Ferguson {Journ. Bombay Nat. 

 Hist. Soc, XV, p. 506). No allusion is made by either of these 

 writers to the occurrence of the bright metallic dorsal band or the 

 silver brilliancy on the sides of this beautiful tadpole. It is per- 

 haps worthy of mention that this tadpole and its congener 

 that of M. rubra are probably most singular in the possession at 

 once of golden and silvery brilliance, of all the Anuran larvae that 

 have been studied up till now. 



