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 Butterfly, 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 
