2Q2 HARRY BEAL TORREY. 



The longer pieces failed to differentiate in these directions, 

 although attempts were made to encourage such developments, as 

 follows : 



1. Nine long heteromorphic segments were held against the 

 aquarium bottom by weighted glass needles laid across their 

 middle. One was cut in two in two days; neither portion had 

 developed frustules twenty-four hours later. One was cut in 

 two in three days; both portions had aboral processes, but no 

 frustules developed in the following twenty-four hours. Four 

 escaped from their needles on the third day, and showed no change 

 at the end of another day. One was almost cut through by the 

 needle, and three processes were formed at the wound, but no 

 frustules or adhesiveness at the end of another day. One re- 

 mained under the needle unchanged for four days, when the exper- 

 iment terminated with my departure from the laboratory. 



2. Discontinuity was produced by ligature on 16 long hetero- 

 morphic pieces two days after regeneration had begun. In two 

 days, 3 had broken into two parts. Two days later, 6 more had 

 done so; the next day, 7 more. Seven days after the ligatures 

 were applied, 2 had frustules at the ligatures. Both were con- 

 tracted and opaque signs of structural degradation; 3 possessed 

 no frustules at the ligature; on the contrary, the proximal seg- 

 ment of one possessed a hydranth there. All the other ligatured 

 pieces had separated into two portions, 18 in all, of which but 4 

 were attached aborally and possessed frustules. 



The first of these experiments serves to emphasize the feeble- 

 ness of contact as a formative influence, while the second adds 

 to the evidence that differentiation in the region between hetero- 

 morphic hydranths depends in an important degree upon the 

 distance between them, which other things equal, is an index of 

 their control. 



That the longer pieces do not show signs of fission, then, is to 

 be attributed, I believe, to the freedom of the intermediate region 

 in each case from the effective control of the physiological systems 

 on either side, that may be conceived as extending over it from 

 opposite directions. Where these systems are near enough to- 

 gether, a new compound system is created, of which a bud may 

 form a part. \Yhen farther apart, their disharmony may appear 

 in the phenomnea of fiisson. 



