LARVAL TELEOSTS 225 
varied and striking of all larval fishes, and, singularly 
enough, appear to be crowded into the briefest space of 
time; the young fish, hatched often as early as on the 
fourth day, is then of the most immature character; it 
is transparent, delicate, inactive, easily: injured; within 
a month, however, it may have assumed almost every 
detail of its mature form. A form hatching three mille- 
metres in length may acquire the adult form before it 
becomes much longer than a centimetre. 
The larval life of the common Sea-bream, or Cunner, 
Ctenolabrus ceruleus, has been admirably figured by A. 
Agassiz. The newly hatched fish (Fig. 303) has the yolk 
sac appended at the throat, as a large, transparent, if 
slightly tinted, globule; save for its great delicacy and 
_ transparency, it may generally be compared to the corre- 
sponding larva of Acipenser (Fig. 296). By the third day 
(Fig. 304), the yolk sac has become greatly reduced, the 
trunk elongated, the fin fold less conspicuous; primitive 
segments have appeared’; the pectoral fin has arisen, but 
is not of the elasmobranch form of the similar stage (Fig. 
298) of sturgeon; it is long, thin, transparent, and its 
rapid growth indicates its metamorphosed character. The 
mouth, S, is in this stage on the point of formation. In 
a slightly older larva (Fig. 305), the yolk has almost dis- 
appeared ; its gill slits, GS, and mouth have now been 
formed, and with the latter the nasal apertures. In a fol- 
lowing stage (Figs. 306, 307), a well-marked opercular fold 
makes its appearance; pectoral fins acquire their com- 
pleted outline and the fin fold undergoes changes: ante- 
riorly it acquires supporting actinotrichia, posteriorly the 
dermal supports of the caudal fin appear and at their bases 
the coalesced radio-basals; a ganoidean heterocercy is 
here apparent, its distal tip the membranous opisthure, O. 
Q 
