208 
COMPAKATIVE ZOOLOGY. 
Coral, when hatched, has six pairs of partitions; after* 
wards, the spaces are divided by six more pairs; then 
twelve intermediate pairs are introduced; next, twenty- 
four, and so on. The embryonic Star-fish has a long 
body, with six arms on a side, in one end of which the 
young Star-fish is developed. Soon the twelve-armed 
body is absorbed, and the young animal is of age. 
Worms are continually growing by the addition of new 
segments. Nearly all Insects undergo complete metamor¬ 
phosis, i. e., exhibit four distinct stages of existence—egg, 
larva, pupa, and imago. The worm-like larva 117 may be 
called a locomotive-egg. It has little resemblance to the 
parent in structure or habits, eating and growing rapidly. 
Then it enters the pupa state, wrapping itself in a cocoon, 
or case, and remaining apparently dead till new organs 
are developed; when it escapes a perfect winged Insect, 
Fig. 172.—Butterfly in the Imago, Pupa, and Larva States. 
or imago. 118 Wings never exist externally in the larva; 
and some Insects which undergo no apparent metamor¬ 
phosis, as Lice, are wingless. The Grasshopper develops 
from the young larva to the winged adult without chang- 
