ALTERNATE GENERATIONS. 237 
means peculiar to the Radiates, but occurs in all 
divisions of the Animal Kingdom. There are 
many Insects that pass through their metamor- 
phoses within the egg, appearing as complete 
Insects at the moment of their birth; but the 
series of changes is nevertheless analogous to 
that of the Butterfiy, whose existence as Worm, . 
Chrysalis, and Winged Insect is so well known 
to all. Take the Grasshopper, for instance: 
with the exception of the wings, it is born in 
its mature form; but within the egg it has had 
its Worm-like stage as much as the Butterfly 
that we knew a few months ago as a Caterpillar. 
In the same way certain of the higher Radiates 
undergo all their transformations, from the Polyp 
phase of growth to that of Acaleph or Echino- 
derm, after birth; while others pass rapidly 
through the lower phases of their existence 
within the egg, and are born in their final con- 
dition, when all their intermediate changes have 
been completed. 
We have appropriate names for all the aspects 
of life in the Insect: we call it Larva in its first 
or Worm-like period, Chrysalis in its second or 
Crustacean-like phase of life, and Imago in ‘its 
third and last condition as Winged Insect. But 
the metamorphoses of the Radiates are too little 
known*to be characterized by popular names ; 
and when they were first traced, the relation 
