LIFE HISTORIES OF CERTAIN FRESH-WATER FISHES. 483 
The Perch \ Perea fluviatilis). Whereas the Pike is from 
the first a solitary fish, the Perch is gregarious. Shoals of 
Perch are common sights in rivers and on lochs where, when 
the water is still the fish can be seen sporting on the surface 
almost like mackerel. The eggs also are laid in long tangled 
skeins amongst the water plants where they look, as some 
one has suggested, not unlike strings of pearls. 
The spawning period of the Perch is from March to May 
and the eggs are easily found in the River An t and in the 
dykes communicating with it. The egg which measures from 
1.7 to 2.0 mm. in diameter and contains a large colourless 
oil-globule about .6 of a millimetre across, is enclosed in 
a dense capsule about .3 of a millimetre in thickness which, 
under the microscope has a striated appearance, the striae 
radiating outwards. The surface view of the capsule shows 
a finely pitted appearance, suggesting that the striae may be 
fine channels allowing the water to pass in after the egg has 
been deposited. A portion of the egg-band examined imme- 
diately after extrusion shows that the yolk and the capsule 
are in close proximity at all points. After a few hours, 
however, there is a distinct space between the yolk and the 
capsule, the egg having become turgid by the absorption of 
water. 
The larvae hatch out in about 14 days, and are almost 
invisible, being quite transparent except for the large dark 
eyes and a few dark chromatophores. The large oil-globule 
lies anteriorly in the yolk which shows segmentation. Within 
24 hours of hatching the larvae measured from 5.0 to 6.0 mm. 
in length, and apparently immediately commenced a gregarious 
existence as they crowded together in the aquarium. The 
pectoral fins were at first not noticeably large, but they seemed 
to grow very rapidly and were apparently much used, as the 
fish are very active. In from 10 to 14 days the yolk sac was 
absorbed, the air bladder had appeared, and the black 
chromatophores had increased in number, being thickly 
grouped along the dorsal region of the gut. a few being 
scattered over the head and body. The dorsal fin was just 
beginning to appear, and in the more advanced specimens 
