last decade, however, a renaissance in the use of hydra as a labora- 

 tory animal has been in progress. 



The return of hydra to their original status as laboratory ani- 

 mals is marked by the pul^lication of Tlie Biolog,y of Hydra : 1961. 

 This is the first book since Trembley's Memoires devoted to original 

 research reports dealing for the most part with hydra. The present 

 volume is a record of a symposium on the Physiology and Ultra- 

 structure of Hydra and of some other Coelenterates held March 29- 

 31, 1961, at the Fairchild Tropical Gardens, Coral Gables, Florida. 



In this symposium. North American workers representing many 

 different fields of biology described their current work. They started 

 with a discussion of the fine structure of hydra cells and mesoglea. 

 Following a session devoted to the development, chemistry, and 

 function of nematocysts, they considered the sul^jects of feeding 

 and nutrition. Next, research on tissue culture, symbiosis, and cal- 

 cification were discussed. A session concerning the various forces 

 responsible for the patterns of colonial hydroids led, in turn, to a 

 consideration of cellular differentiation and then of aging in both 

 mortal and immortal coelenterate types. Appropriately, attention 

 turned at last to regeneration and to new birth as seen in budding. 



In organizing this symposium, the editors desired to bring about 

 an integration of knowledge from a large variety of disciplines. 

 Electron microscopists, naturalists, biochemists, and developmental 

 biologists ordinarily do not read or publish in the same journals. 

 The aim of the symposium was, therefore, to effect an interdisci- 

 plinary synthesis which might otherwise take years by normal chan- 

 nels. Accordingly, the discussions that followed each talk are 

 included because they point out some of the many unsolved prob- 

 lems and therefore should prove of value in stimulating further 

 investigations. 



Much of the work presented at this symposium is in an early 

 stage. At times we have thought that perhaps these results are 

 too preliminary and should only be compiled after more data have 

 been accumulated. The situation is analogous to constructing a new 

 building. At times we might feel that all such work should proceed 

 behind walls marked "Work in Progress. No Admittance." At other 

 times we are intrigued with the very smell of sawdust and of wet 

 paint. It is in this latter spirit that the volume was compiled, for 



