1/4 MAX MORSE. 



while the hydranth lies at the bottom of the dish, completely 

 severed from the stem, the tentacles are seen to move about as 

 in a normal individual. After a longer or shorter time, varying 

 with external conditions, the movements cease, the hydranth be- 

 comes whitish and evidences of disintegration become apparent. 

 The ccenosarc of the stem, on being freed from the hydranth, 

 early shows a collection of red pigment, described by Driesch, 

 Loeb, Stevens and Morgan in their studies of regeneration in this 

 genus. The tube of the stem has been closed distally by the 

 folding and compression of the walls even before the hydranth 

 has been lost. For ? time immediately after the autotomy of 

 the hydranth has taken place, the ccenosarc withdraws for one 

 of two millimeters down the perisarc tube, leaving free, ragged 

 edges to the outer tube projecting beyond the protoplasmic 

 portions. Soon, however, the ccenosarc is seen to be flush with 

 the top of the perisarc. 



Sections through hydranths and stems at the period when the 

 hydranth is falling, show a constriction of the protoplasmic parts 

 immediately beneath the attachment of the hydranth to the stem. 

 The perisarc seems to take no active part in the changes involved 

 in autotomy. The walls of the coenosarc, involving both ecto- 

 derm and entoderm, are folded upon themselves. In some 

 specimens there seems to be an indication of histolysis setting in 

 among the cells forming the ectoderm and entoderm in the por- 

 tion of the coenosarc tube involved in the constriction. When 

 it occurs, such dissociation of the cells is of local occurrence only 

 and is to be found only in the constriction. Examination of the 

 hydranth in such cases (Fig. i), shows it to be perfectly normal 

 as far as one may judge from histological evidence. Moreover, 

 living specimens, as has been mentioned, show activity of the 

 tentacles even after the hydranth has been removed. 



For a time, varying with the individual, the hydranth remains 

 attached to the stem by the perisarc only and it is the weight, 

 probably, of the hydranth which ruptures the chitinous perisarc 

 and frees the hydranth from the stem. One may see, in the 

 individuals at this stage, resting in the aquaria, that all proto- 

 plasmic attachment has been withdrawn and longitudinal sections 



