Regeneration in Hydroinedusae 3 



etc., but in general the best results were obtained with iron- 

 hematoxylin. 



IV. Experimental Work 



I. REGENERATION 



From his work on Antennularia antennina, Loeb (1893, p. 42) 

 drew the following conclusion : '-In Antennidaria gravitation 

 not only determines the place of origin of various organs, but 

 also the direction of their growth." He states that rhizoids grow 

 from the lower side or end, and hydranths from the parts directed 

 upward, regardless of the position of the stem. Driesch (1897), 

 working on Antennularia raniosa, found that other factors be- 

 side gravity influenced the regeneration. Morgan (1901) found 

 for A. rainosa that roots usually form at both ends. He sug- 

 gests, however, that "the development or presence of roots on 

 the basal end prevents development of roots on the apical end." 

 Stevens (1902), working on the same form, concludes that the 

 kind of regeneration is determined neither by the polarity of the 

 piece nor by "orientation with respect to gravity," nor by con- 

 dition existing at the other end of the piece ; but that certain 

 parts of the stalks show a tendency to form roots and other 

 parts to produce stems. 



To determine whether gravitation had any effect on the regen- 

 eration in Tubularia crocca, I took pieces with branches and 

 placed the distal end of the main stalk in sand. The piece was 

 fixed so that the ends of the branches cleared the sand and were 

 entirely surrounded by water. In no case did stolons form, though 

 hydranths formed quite rapidly and readily. It was further 

 noted that hydranths formed sooner on the ends of branches, 

 whether they ejstendedjaterally or downward, than they did on 

 the ends of the main stems which pointed directly upward (fig. 

 5). This would seem to indicate quite clearly that gravity has 

 no influence on the regeneration in this species, at least on the 

 regeneration of the stems, and furthermore that regeneration 

 of hydranths occurs more rapidly at the distal ends of stems. 



Loeb (1893) also states that in Margelis and Peimaria the kind 

 of regeneration and the direction of growth are determined by 



277 



