274 Records of the Indian Museum. [Yor XT 
The embryonic and larval development of this species closely 
resembles that of O. stviatus,' but is more rapid. In fresh eggs 
the outline of the embryo encircling the yolk becomes evident in 
about 8 hours; the eyes and auditory sacs are developed in 16 
hours; and the heart begins to beat and the curious yolk-sac 
circulation also starts soon after this (figs. 19 and 20). At the 
time of hatching the embryo violently twitches its tail, which is 
now free of the yolk-sac, and performs rotations within the egg- 
membrane. 
On hatching the fry measure 3'25 mm. in length and are 
almost identical in general appearance with the first day hatch- 
ings of O. striatus (fig. 21). They, however, do not remain at 
the surface for 3 days like the latter fry but begin to descend 
down even at the close of the first day, though this is accomplished 
with considerable effort. 
On the second day, the pigment cells are well developed, the 
eyes being quite black ; the length increases to 42 mm. ; the mouth 
opens and respiratory movements begin; and the pectoral fins 
develop. The larve move in unison and effect their descent from 
the surface in a long procession, swimming slowly close to the 
bottom sand of the aquarium. Most of the above changes are 
those of the 3rd day in the development of O. striatus. 
On the third day, the fry swim at all levels with ease. On the 
sides of the body the mid-lateral line is clear of pigment, but pig- 
ment is intense along the root of the dorsal and ventral portions 
of the median embryonic fin. During the second and third days 
the capillary network formed by the caudal vein in joining the 
subintestinal vein, and the ‘‘ marvellous yolk-sac circulation ’’ 
described by Dr. Willey, arise in the same way as in O. striatus. 
On the fourth day (fig. 22), the length is 5mm. ‘The charac- 
teristic black and yellow colour of the fry, which distinguishes 
it from the brown and pink fry of O. striatus, now begins to 
appear. 
It will be seen from the above observations that the larval 
development in this species, while it closely resembles that of 
O. striatus, goes forward more rapidly. This is true of most of 
the subsequent stages, such as the formation of the network of 
vessels at the root of the caudal fin (which happens about the 
eighth or ninth day instead of on the twelfth as in O. striatus *); 
the deflection of the end of the notochord, the commencement of 
aerial respiration, etc. 
Characteristic colour of the young® (fig. 22).—The character- 
istic larval colouration begins to appear as early as the fourth 
day after hatching. On the sides of the body, as noticed above, 
pigment is intense along the root of the dorsal and ventral por- 

1 Willey, ‘‘Nests, eggs and larve of Ophiocephalus striatus.’ Spol. 
Zeylan., V1, pp. 108-118 (1909). 
2 Willey, Spol. Zeylan., VI, p. 112 (1909). 
> Willey, Spol. Zeylan., V, p. 150; VI, p. 116. 
