392 LIBBIE H. HYMAN. 



formed hydranths as compared with i, 6, and less than 15 basal 

 pieces in the control experiment, number 10, Table III., when 

 6, 1 6, and 25 apical pieces have regenerated in both cases. 

 Similarly, in experiment 30, for which experiment 26 is a control, 

 the regeneration of the apical and basal pieces is practically 

 simultaneous, a result which is never obtained when stems free 

 from branches are employed. Comparison of experiment 36, 

 Table VIII., with its control, experiment 35, Table IV., shows 

 the same effect; in the former case 12 basal pieces, in the latter 

 case no basal pieces have regenerated at the time when 18 apical 

 pieces have regenerated in both experiments. In other cases, 

 as in experiment 34, little difference from the control could be 

 observed. The decrease in the time difference between the 

 apical and basal pieces in these experiments is apparently largely 

 due to a delay in the regeneration of the apical pieces. This is 

 to be expected, since as already explained all basal pieces are 

 probably more or less isolated as new individuals, and hence 

 are slightly accelerated in both experimental and control series. 

 The "apical" pieces, on the other hand, in the present experi- 

 ments, since they are taken in front of the level of a branch, really 

 represent the basal end of the first zooid of the stem, and hence 

 are delayed in regeneration as compared with pieces similar in 

 position from stems where branches have not yet arisen and where 

 the hydranth still controls most of the length of the stem. In 

 regard to the basal pieces, it should further be pointed out that 

 the really high metabolic point of the new individuals formed at 

 the base of Tiibularia stems is in the hydranth of the branch, 

 and the basal piece itself below the level of the branch retains 

 only part of the increased metabolic rate after the bud has 

 formed. 



Banus has presented one table in which he has compared the 

 rate of regeneration of three equal pieces, each 10 mm. in length, 

 from different levels of the same stem. I have not repeated these 

 experiments as they seem to be lacking in point. The reason 

 why the apical pieces in these experiments of Banus regenerate 

 more slowly than the middle pieces is doubtless, as in the case 

 of the other experiments reported in his paper, the consequence 

 of an erroneous method of cutting the apical pieces. That some 



