48G MR. F. BALFOUR BROWNE ON THE EARLY STAGES IN THE 
the rather thick capsule which is covered with small 
tubercles. 
The eggs hatch in less than io days, but I was not fortunate 
enough to notice the newly hatched larva. My illustration 
is of a fish which has been hatched at least three days, as the 
heart is in a horizontal position, and the yolk sac is almost 
absorbed, and the gills and mouth are developed. The yolk 
sac in the newly hatched larva was apparently flask shaped 
as in the Bream. 
Lack of time prevented my paying further attention to 
these two species which were left to themselves mixed in an 
aquarium. After a fortnight the Bream had all disappeared, 
but most of the Roach survived until August when they were 
set free in the Broad. 
The only other species which I hatched and reared was the 
Nine-spined Stickleback ( Gasterosteus pungitius) whose eggs, 
and those of the three-spined species (C. aculeatus), are to be 
found in the dykes from the end of March until the beginning 
of June. The eggs are adherent in a mass, and are deposited 
by several females in a nest constructed out of water plants 
by the male, who also guards the eggs until they are hatched. 
A Stickleback egg measures about 1.5 mm. in diameter, 
and contains a number of small colourless oil-globules. I did 
not try to obtain eggs from the females although ripe fish of 
both sexes were easily obtainable, but I obtained any number 
of eggs in which development had only just commenced. 
Such eggs took from 12 to 20 days before the larvae hatched. 
The newly hatched larva which measures about 4.9 to 5.0 mm. 
in length, is colourless except for a few black chroma tophores 
on the head and in the dorsal region of the gut. There are 
also 7 or 8 well marked pigment patches along the dorsum 
which together with some on the gut appear pale yellow when 
viewed by reflected light. The eyes also are well pigmented 
from the first. 
The yolk sac presents a striated appearance owing to the 
presence of numerous blood vessels which at first contain 
colourless blood. These vessels all converge towards the 
anterior and lower end of the yolk sac and pass forwards to 
