356 Florence Peebles 



visible externally, but they exert some influence on the rest of the 

 pieces, whether they result in the formation of new structures 

 or not. 



2 When the aboral end of a piece of the stem of Tubularia is 

 stimulated through grafting to produce a hydranth before the oral 

 end, the change in the polarity is not lasting for when a second set 

 of hydranths develop, the piece assumes its original polarity. 



3 When a short and a long piece are grafted together the 

 influence of the longer piece is shown only when the new hydranth 

 comes from the two pieces, a row of tentacles forming in each. 



4 Short pieces grafted together in any direction usually develop 

 a hydranth on one of the free ends only, or first on one end and 

 later on the other. The result is the same whether the currents 

 in the two pieces are continuous or not. 



5 If the tip is removed from the end of a stem on which a new 

 hydranth has just begun to develop, before the ridges are visible, 

 the small piece is capable of forming a complete hydranth. If 

 the tip is removed after the ridges are laid down, the piece devel- 

 ops one row of tentacles. The proximal piece completes itself 

 distally by forming new tentacles on its tip, either before or after 

 emerging from the perisarc. If the tip is removed before the 

 primordia appear the proximal piece usually forms new primordia 

 without delay. 



6 If, after the appearance of the primordia, the piece in which 

 the distal row of tentacles develops is reversed and grafted back 

 on the proximal row, the hydranth completes itself in the normal 

 manner. Sometimes the distal piece develops a new row of distal 

 tentacles in front of the original red ridges which persist after the 

 hydranth emerges. 



7 When the entire primordium is removed by a cut just below 

 the base of the proximal tentacles, the ridges frequently fade out 

 and a new primordium develops which is much shorter than the 

 original one. A cut 2 to 3 mm. below the primordium does 

 not affect its later development. Such pieces do not form aboral 

 hydranths. 



8 Diluting normal sea-water in which pieces of Tubularia are 

 placed, increases the rate of growth and the percentage of new 



