120 



temperature of the waters of the primeval seas, inasmuch as 

 the two groups of Zoophytes are constructed on essentially 

 different types." 



On the contrary, I beHeve, there is abundant evidence for 

 concluding that like conditions prevailed wherever reef-building 

 Corals worked; for the associated MoUusca Trigonice, in the 

 secondary, and Echinoderms Crinoidioe in the palaeozoic rocks, 

 point to tropical seas as the true home of these animals. 



The palffiontological history of the Actinozoa yields results 

 perfectly analogous to those offered by other classes of the 

 animal kingdom. 



1. — The genera and species of each of the great groups into 

 which Zoologists divide these animals have had a limited 

 duration in time and space, — no genus of the Palaeozoic epoch 

 having been found in any of the subsequent epochs, and no 

 living genus having been discovered in rocks older than those of 

 the Jurassic period. 



2. — There is no evidence of any gradual development having 

 taken place in this class from a lower to a higher type of 

 Coralligenous structitre ; the old Corals of the ancient reefs 

 appear to have been as highly organised, and as elaborately 

 constructed as the modern Corals, now building reefs, in our 

 tropical seas. 



MM. Edwards and Haime have made most important and 

 acciu'ate studies on the structure and development of Corals, 

 and have embodied their observations in a series of valuable 

 memoirs.* From these we learn that the term Gorallum is 

 employed to designate all that distinct mass formed by the hard 

 parts of one or many Polyps, united organically together, and is 

 synonymous with Polypidom or Polypary, signifying the hard or 

 calcified parts of the body of the animal or Polyp, possessing 

 a radiate structure, a protractile mouth, surrounded by non-ciliate 

 tentacula, and a large well-organised digestive cavity, but no 

 vent. 



The Sclerenchyma, or hardened tissue of Polypi by which 

 Corals are formed, is always a portion of their tegumentary 



• Annales des Sciences Naturelles, 3me. sferie, torn. ix. 



i 



