296 HARRY DEAL TORREY. 



the distal hydranth, and has apparently developed later, below 

 an interruption in the physiological continuity of the column 

 comparable with what a ligature might produce. In fact, just 

 such cases have been produced experimentally several times. 

 A typical experiment may be recorded, showing incidentally the 

 difficulties that made the number of positive cases so small. 



The column of Corymorpha is very mobile, capable of con- 

 siderable changes in length and bulk, and its tissues are very 

 delicate and easily ruptured. So it has been difficult to make 

 ligatures tight enough to interrupt the currents in the canals, 

 as well as possible diffusions through the axial cells, without so 

 weakening the column as to lead to complete rupture in two or 

 three days. This has been accomplished, however, in a number 

 of cases sufficient for the present purpose. 



EXPERIMENT i. 



April 29, 1910, 3.30 P. M. Sectioned 20 polyps of similar size, 

 about midway of the column, and ligated each just below 

 wound, leaving a small segment of tissue above the ligature. 



May i, 9.30 A. M. Four stumps removed, ligature having come 

 away with terminal button of tissue. 



May 2, 5 P. M. Thirteen more removed for similar reason. 

 There are hydranths on these stumps that seem to be too far 

 along, under the conditions, for 31^/2 hours (i. e., assuming 

 the separation to have occurred immediately after the previous 

 survey of them, which is not probable). 



Of the remaining 3, 2 show nothing below the ligature, 

 while the third appears as in the semi-diagrammatic Fig. 17, 

 which bears a striking resemblance to Fig. 16. 



May 3, 9.45 A. M. The two hydranths of Fig. 17 have fallen 

 apart. 



May 4, 10.00 A. M. Of the 2 stumps showing no development 

 below the ligature of May 2, one (a) has now budded a set of 

 tentacles just below the ligature; the other (b) as before. 



May 6. The tentacles of (a) are larger. 



May 9. Still no change in (b). Exp. abandoned. 



In a second experiment, 6 columns were tied as indicated in 



the diagram (Fig. 18, a), after removal of hydrant li. 



