220 Records of the Indian Museum. [Voh. XVI, 



Stage III. — This is a much more advanced stage than the last 

 one. Some of the larvae have already hatched out while others 

 are still enclosed in the egg-capsule. In hatching, the free 

 posterior portion of the body and the tail (both of which are well 

 developed) are the first to come out of the egg-capsule. The head 

 and the rest of the body, with the large yolk-sac, are then separa- 

 ted out by violent movements of the tail. vSome of the larvae 

 show the body still enclosed in the egg-capsule but have the 

 tail protruding. 



In this stage only a part of the head is free, the rest 

 is very closely applied along the ventral surface to the yolk-sac, as 

 shown (to some extent) in fig. 7. The mouth is present as a 

 distinct, horizontal slit and the opercular Hmits are also marked, 

 specially on the ventral surface. The head, which has not 

 developed to any great extent as yet, is broadest in the region of 

 the hind brain. This latter structure is well developed, and shows 

 the large cerebellum getting marked from it. The pectoral 

 fins are just appearing and the continuous dorso- ventral fin 

 has, besides increasing in size, begun to show rudiments of the 

 fin-rays, in the caudal region. The supporting elements of 

 the fin-rays ( or pterj'giophores ) are already well developed. 

 There is nothing particular to note about the sense organs 

 except that the external narial opening is well developed. The 

 gill slits are well advanced and the arches show traces of the 

 development of gill filaments on them. The air-bladder is 

 elongated and sac-like, measuring about r"2 mm. in length, it 

 shows no constriction. 



Stage IV (fig. 8).— The mouth, which was ventral in the 

 last stage, has, owing to the separation of the head from the yolk- 

 sac and the better development of the middle portion, shifted to a 

 position far forward and is now more or less anterior. The head 

 is becoming marked off as a prominent structure owing to the 

 special development of the optic lobes and the cerebellum The 

 eyes are now partly enclosed in the optic capsules and do not 

 protrude as much as in the last stage. The pectoral fins are 

 better developed and the fin-rays are making their appearance 

 both in the pectoral and in the anal fin-portion of the dorso- 

 ventral fin. The yolk-sac is being gradually absorbed and 

 has become transformed from a rounded to an ovoidal structure. 

 The gill filaments are better developed and even gill-rackers are 

 developing on the arches. The outline of the jaws is also 

 indicated. 



Stage V (fig. 9). — This stage, except for showing the beginning 

 of the dorsal fin, is very near the last one. The various 

 organs, however, are better developed and there is a distinct 

 increase in size. 



Stage VI. — This stage has still a fairly massive yolk-sac. It 

 shows the operculum quite separated as a flap on either side and 

 forming the posterior limit of the head. The flexure of the brain 

 is better marked, and the medulla oblongata is much better 



