412 



I . II. IIVMAN. 



middle third next, and the basal third last, the differences be- 

 tween the three pieces being well-marked. The basal third in 

 T. marina is generally much behind the other pieces. A typical 

 experiment on T. marina is given in Table II. On the contrary 

 in the Maine species, the time between cutting and emergence 

 of hydranths is about the same for the middle and basal thirds, 

 the apical third being in advance as usual. I have, however, 

 but five sets of pieces in which the time of emergence of the oral 

 hydranths was exactly determined in all three pieces. These 

 times are as follows, apical third first, middle third next, basal 

 last: 39, 45, 46 hours; 41, 52, 52 hours; 42, 53, 53 hours; 43, 50, 

 53 hours; and 41, 46, 46 hours. These pieces were 8 to 10 mm. 



long. 



TABLE II. 



REGENERATION RATE OF HALVES AND THIRDS OF THE STEM OF Tubularia marina. 



The first column gives the hours elapsed between cutting and emergence of the 

 oral hydranths; and the other columns the number of hydranths emerged at the 

 hours indicated. Length of halves, 3-7 mm.; length of thirds, 5-8 mm. 



It thus appears that the physiological differences along the 

 stem which are responsible for the differences in regeneration 

 rate at different levels extend further down the stem in T. 

 marina than in either of the Atlantic coast species. Banus ('18) 



