84 THE EVOLUTION OF CONTINUITY 



Megazooidal Individuals may be classed as follows : — 



(1) The Mono-megazooidal Individual, of which our 



examples are the Sea-anemone and the Indi- 

 vidual Medusa or Jellyfish (there are jellyfish 

 which are not Individuals). 



(2) The Discontinuously Megazooidal Individual, the 



example taken being one of the Acraspeda. 



(3) The Continuously Megazooidal Individual, exem- 



plified by the Compound Corals generally. 



ID 

 a 



u 



J c 



Fia. 20. — Diagram of the evolution of living Continuity, 

 beginning with the separate cell and stopping at the mega- 

 zooidal colony, a, a free protoplast ; 6, a cell -filament, a 

 multiple of a in serial Continuity ; c, the Continuity of b 

 multiplied into the lateral Continuity of the discontinuous 

 zooid ; d, zooidal serial Continuity ; e, the free megazooid, 

 equivalent to a number of zooids compressed in lateral Con- 

 tinuity; t, megazooidal serial Continuity. The figured are 

 very diagrammatic. 



We shall begin by considering the Sea-anemone and the 

 Medusa. 



The Mono-megazooidal Individual of Sea-anemone 



Type. 



The general appearance of the Sea-anemone is familiar 

 to everyone. When its tentacles are extruded, the little 

 animal has the form of a short broad cylinder. The mouth 

 is a contractile opening centrally placed in the circular 

 surface of the upper or distal end, while marginally placed 

 are numerous strong tentacles in several rows. The base 



