4'4 I.. II. IIYMAN. 



of pieces 2 mm. in length, for instance, runs far behind that of 

 longer pieces. 



4. Relation of Rate of Regeneration to the Diameter of the Stem- 

 It was previously reported that the time between cutting and 

 emergence of oral hydranths is noticeably shorter the more 

 slender the stem. This was again verified on the Maine species. 

 It is reasonable to believe that this result is correlated with the 

 fact, given in the first part of this paper, that the rate of oxygen 

 consumption is higher, the less the diameter of the stem. 1 



5. Relation of Size of the Regenerated Oral Hydranth to the 

 Length of the Stem. A number of measurements were made both 

 at Woods Hole and Swan's Island of the size of the regenerated 

 hydranths on stems of the same distal diameter and cut at the 

 same distal level but of different lengths. Measurements were 

 made with an ocular micrometer, and on the fully expanded 

 hydranth some hours after emergence. The length of the ten- 

 tacles, the length of the body (distance from tip of manubrium to 

 constriction just below base of hydranth), and width of the 

 widest part of the hydranth (part bearing the proximal tentacles) 

 were measured. The most extensive experiment of this kind 

 was done at Swan's Island. A number of pieces having the same 

 apical level but of different lengths and diameters were cut and 

 placed in one bowl. After regeneration the dimensions of the 

 regenerated oral hydranths and of the original piece were taken. 

 These data are given in Table III. and are arranged with reference 

 to the diameter of the apical end of the piece. 



These data show that the dimensions of regenerated oral hy- 

 dranths are about the same on pieces of quite different lengths 

 but of the same diameter and with their apical ends at the same 

 level. This statement would probably not apply to very short 

 pieces (under 2 mm.) but as shown in the table pieces as short as 

 2 mm. may regenerate hydranths as large as those from pieces 

 several times as long. Some of the longest pieces may produce 



1 Stems whose diameter is smaller are of course also smaller in other particulars 

 total length and size of hydranths. As pointed out later they are simply younger 

 as a rule than larger stems. It seems convenient to take the diameter of the stem 

 as a measure of age. Wherever it is stated throughout this paper that the diameter 

 of the piece is smaller it is to be understood that such pieces were taken from stems 

 of general small proportional 



