Regeneration in Hydroinedusae li 



crushed the stem very Httle if at all. The cut pieces were then 

 placed in petri-dishes, watch glasses, etc., filled with fresh sea 

 water. The cut surfaces were carefully brought into as close con- 

 tact as possible and held in place by pieces of freshly shaven lead. 

 Th» hydranths were removed in all cases, as the movements of 

 liydranths and tentacles would destroy the close contact of the 

 pieces. As soon as the pieces had stuck together, the lead was 

 removed and the pieces allowed to develop freely. In Endcn- 

 driuni and Pennaria the pieces were very soon held firmly in 

 place without the lead, because of the holdfasts developed from 

 the ends of the stems and branches in contact with the glass. 

 After the coenosarcs had united a new perisarc was secreted over 

 the point of union. In Tnbnlaria crocea union was complete in 

 from 18 to 24 hours. At the end of this time the circulation of 

 fluid could be observed taking place betv^een the two pieces. In 

 the uniting of the coenosarcs the pieces were often pushed apart 

 slightly (fig. 4). However, a new perisarc was soon secreted over 

 this and the woimd entirely covered. The formation of hydranths 

 took place quite rapidly after union was complete, sometimes 

 forming at both ends. Endendrinni usually united in 24 hours, 

 though hydranths were not fully formed till 24 to 48 hours later. 

 The method of union was similar to that of Tnbnlaria, and 'new 

 perisarc was formed over the point of union (fig. i). The graft- 

 ing of Endendrinni and Pennaria was tried, but no union took 

 place, the coenosarc of Pennaria forcing itself out into stolons 



(%-9)- 



In Pennaria Ihe time necessary for complete union was from 



24 to 48 hours. Hydranths developed slowly, not being fully 

 formed till 24 to 48 hours later. A teature quite common in 

 the grafting of Pennaria was the formation of stolons from the 

 point of contact of the two pieces (figs. 2a, 2b). Pennaria found 

 growing on the piles of docks was successfully grafted with Pen- 

 naria from floating eel grass, though, as already mentioned, the 

 habits of the two were quite different. 



285 



