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 



