58 RE GENERA TION 



endoderm, draws away from the chitinous perisarc, as shown in Fig. 

 28, B. A hydranth with a short stalk is then produced. In other cases, 

 Fig. 28, C, almost all of the coenosarc is used up to form the hydranth, 

 and only a short, dome-shaped knob represents the stalk. In still other 

 cases there may be no stalk at all (Fig. 27, Z>), but only the hydranth. 

 Forms like the last two are more often produced from pieces of the 



G 



FIG. 28. Tubularia mesembryanthemum. Products of regeneration of short pieces. A. Piece 

 that regenerated a hydranth in same way as do longer pieces, but with fewer tentacles. 

 B. Pieces whose stem drew away from wall of old perisarc (cylinder in figures). C. Hydranth 

 with almost no stalk. D. Hydranth without stalk. JS. Distal part of hydranth with one long 

 proximal tentacle. E l . Similar, but more reduced. E"*. Similar, with two tentacles at side. 

 F. Proboscis with reproductive organs. G. Proboscis without reproductive organs. 



distal end of the stalk. From very small pieces, forms like those shown 

 in Figs. 28, E-E 2 , that represent only proboscides with a reduced 

 number of tentacles, are sometimes formed. Reproductive organs 

 may be present at the base of these pieces. A further reduction is 

 shown in Figs. 28, F, G, that are proboscides with only the distal circle 

 of tentacles ; in one of these, reproductive organs are present around 

 the base. Partial forms more reduced than these have not been found. 



