3 86 



Memoirs of the Indian Museum. 



[Voi,. V ; 



The ' ' concentration ' ' of the body segments has not yet taken place except at the 

 anterior end. 



The dorsal, caudal, and anal fin-folds are continuous (a primitive character). 

 Furthermore, the skeletal supports of the fin-folds are either not yet developed or if 

 developed (there are faint indications of the development of the fin-rays towards the 

 caudal end) are not visible even under the high power of the microscope. The pelvic 

 or ventral fins are not yet developed. The pectorals are short and contain 9 fin-rays. 



The pigments are a characteristic feature of the larva. There are eleven fairly 

 big black stellate chromatophores in the anal fin-fold from about the middle of the 

 body to the base of the caudal fin-fold. There are also scattered but rare small brown 

 (or in places blue black) pigment spots both in the dorsal and anal fin-folds. The 

 caudal fin-fold is practically free from pigments. At the distal extremity of the 

 pectoral fin beginning from about the middle, pigments of a deep blue black colour 

 are very densely situated. 



The posterior region of the alimentary canal and anus are visible. A short 

 opercular spine and a frontal protuberance are developed. The notochord is well 

 developed and extends to the tip of the tail end. 



Slightly older stages than these are available. They show a slightly heterocercal 

 tail fin. The caudal fin-rays in these have just begun to develop, but are not yet 

 segmented. In the anal fin-fold the number of chromatophores varies from 12-15 in 

 number. 



Plate xvii, fig. 9 (stage II) measures J.325 mm. in length (including the middle 

 caudal fin-rays). This is a much more advanced stage than fig. 8. The myotomes 

 are well developed, and the myocommas are quite distinct. The longitudinal 

 horizontal septum separates the epiaxial from the hypaxial portion of muscle segments. 



The fin-folds have become discontinuous and we get a long dorsal, a caudal, and 

 a long anal fin. The diphycercal and heterocercal stages have been passed through, 

 and we get the homocercal type of fin characteristic of the adult. The caudal fin 

 consists of 22 jointed fin-rays and is practically free from pigments. The ventral fin is 

 short and slender and lies anterior to the pectorals on the ventral side of the body. 

 It consists of 2 fin-rays only. The pectorals are composed of 13 fin-rays, and are 

 deeply pigmented (blue black) towards the distal end. The dorsal and anal fins are 

 composed of spinous rays which will be described in detail in the next stage. On 

 each side of the dorsal and anal fins, and closely attached to them is a membranous 

 fin-fold in which lie a row of pigments or chromatophores (fig. 9 i). The stellate 

 chromatophores of fig. 8 are lost at this stage. 



The frontal prominence and narial tentacles are developed. The eyes are well 

 developed and acquire deep pigments. Two (only) opercular spines, one on each side 

 of the body, are developed, their extremities having a curiously bent shape. Whether 

 this is their natural condition or is due to injury (which seems more likely), I cannot 

 say, but all the available medium-sized and large specimens (6 only in number) showed 

 this bent condition. The pigments of the brain are visible dorsally through the 

 cartilaginous cranium and the various elements which compose the adult skull are as 



