Regeneration 



179 



grow, moreover, exactly at right angles to the solid 

 surface element to which the stolon is attached. If such 

 a stem be cut and put into a watch glass with 

 sea water, it can be observed that those polyps 



which do not fall 

 off go through a 

 series of changes 

 which make it ap- 



pear as if the dif- 

 ferentiated material of the polyp were 

 transformed into undifferentiated ma- 

 terial. The tentacles are first put to- 

 gether like the hairs of a camel's-hair 

 FIG. 34 brush (Fig. 34) , and gradually the whole 

 fuses to a more or less shapeless mass 

 which flows back into the periderm (Fig. 35). It 

 follows from this that in this process certain solid 

 constituents of the 

 polyp, e. g.j the cell 

 walls, must be 

 liquefied. This un- 

 differentiated mate- 

 rial formed from the 

 polyp may afterward 



flow out again, giving rise to a stolon or a polyp ; to the 

 former where it comes in contact with a solid body, to 

 the latter where it is surrounded by sea water. These 

 observations suggest the idea of reversibility of the 



FIG. 35 



