LARViE, ETC., OF OPHIOOEPHALTJS STRIATUS. 
Ill 
and do not know for certain whether the eggs of this species float at 
the surface like those of “ lula,” or whether they lie at the bottom 
like those of most other freshwater fishes. I hope to clear up this 
point at an early date. 
On June 1 still another lot of ‘ 4 lula” eggs was brought in from 
Welikada, near the toll-bar on the road to Kotta near Colombo. 
The material upon which this paper is based has thus been derived 
from four broods, namely, one from Minneriya, two from Hunupitiya, 
and one from Welikada. 
The floating eggs of e 4 lula ” owe their buoyancy to the presence of a 
single large oil-globule which occupies the greater part of the ovum 
and is immersed in the golden yellow yolk (PI. II., Fig. 1). It is 
adjacent to the upper pole of the egg, and in surface view under a 
low power of the microscope is seen to be surrounded by a narrow 
zone of the yolk, the whole being contained within a space bounded 
by the vitelline membrane (Fig. 2). As the eggs lie immediately 
below the surface film of water exposed to the quickening influence 
of air and sun, the intravitelline or embryonic development goes 
forward rapidly ; although I have not been able to time this period 
accurately it would appear that hatching takes place within three 
days after oviposition, and perhaps within twenty-four hours. 
From the condition represented in Fig. 1, as seen with a simple lens 
at 5.30 p.m., we reach overnight the stage shown in Figs. 3 and 4, 
where the body of the embryo encircles about two-thirds of the yolk 
like a belt. The surface view (Fig. 4) shows that while the head is 
still appressed to the yolk, the tip of the tail is becoming folded off ; 
the eye and auditory vesicle are also present. 
A few hours later the heart begins to beat and the tail to twitch. 
The orientation of the embryo is constant, the left side being upper¬ 
most when viewed from the upper pole of the egg (Figs. 4 and 5). 
The movements of the tail soon lead to the rupture of the vitelline 
membrane and the liberation of the embryo ; and now commences 
the larval period of development The eggs retain their glistening 
oily golden yellow lustre up to the moment of hatching, but before 
this event the outlines of the future pigment cells can be seen upon 
the surface of the yolk under the microscope. The pigment does 
not become obvious until some hours after hatching. 
The general appearance of a young first day “ lula ” hatchling is 
shown in Fig. 6. It measures 3*5 mm. in length ; the microscope 
only reveals very faint pigmentation, and the eyes are destitute of 
pigment. There is a wonderful yolk-sac circulation ; the anterior 
cardinal vein is seen issuing from the head behind the auditory 
vesicle and passing across the front part of the yolk-sac to join the 
sinus venosus. The caudal vein pours its blood into the subintes- 
tinal system, which is joined by the posterior cardinal vein at the 
level of the angle contained between the projecting yolk-sac and 
r 7(14)09 
