BERNARD L. STREHLER 



39? 



Fig. 1. Sketches to illustrate Nathanson's experiment. A. An isolated 

 hydranth. B. The hydranth may produce a short stolon in a few hours. C. 

 When regression of the hydranth occurs the stolon grows. D. A new upright 

 has started to form; regression of the old hydranth is nearly complete. E. A 

 new hydranth is produced. 



lapse or become buried under the increased weight. However that 

 may be, I beheve all reef corals are clones. 



STREHLER: Studies on the incorporation of tritiated thymidine 

 into the DNA of Metridium or of other long-lived forms would be 

 of interest in outling the pattern of cell division and replacement. 



CROW ELL: May I go back to what we were talking about this 

 morning? How, and in what form, are materials moved to regions 

 of growth? These sketches, Figure 1, show the results obtained by 

 Nathanson (Nathanson, D. L. 1955. The relationship of regener- 

 ative ability to the regression of hydranths of Campamdaria. BioL 

 Bull. 109: 350). He cut off single hydranths of Campanularia, placed 

 them in stender dishes, but did not feed them. A hydranth merely 

 sat for from one to four days. In some cases it produced a little bit 

 of stolon, as shown in Figure IB. When a hydranth began to regress 

 the stolon elongated, as shown in C and D, then it sent up a new 



