BIOLOGICAL STUDIES ON CORYMORPHA. 293 



These statement- are <>b\ -ioiisly very general. Since all short 

 heteromorphic pit-re- <\ not either hud or divide by process of 

 h--i(ni. ilicn- mu-t IK- a factor still undefined that determines the 

 la< k <-f uniformity. There is no doubt thai external a^encie- 

 i an fai ilitaii- either budding or fission. Small \\ound- in the 

 -ide ut' tin- column may lead to a variety of rc-ult-. including 

 sporadic tentacles, and buds furni-hcd \\ iih ti-ntai le- >v tru-tule-, 

 or neither. In this connection two heteromophic piece-, cut in 

 the middle region, hall" way through the column, ga\e the tol- 

 louing results. On the longer piece, a narrow bud de\ eloped 

 in four da>- at the wound, with neither fru-tule- nor tentacle-. 

 ( )n the -horter piece, frustules developed around a blunter bud 

 at the \\oinnl, before attachment took place. In thi- the 



\\ound ua- -iilticicnt to break up the original -\-tem exi-tmg 

 at that point and initiate a ne\\ de\ elojnnent . The tact thai 

 fru-iule- appeared shows the control of both h\dranlh- on that 



de\ elopinellt . 



I '. lidding OC< in -, ho\\ e\ er. \\ hen t here i- no -i^n . .| local injury 

 I loin \\ ithout . And it i- ditfn ult to aC( oimt on thi- ^louiid alone 

 for the fact that the large niajoritx of luid- aii-e appn >\imatel\- 

 nii.luax b-t \\eeii the hydranths. To m\ mind, far more -signifi- 

 cant i-s the fatt that buds develop so of ten on pieces obviously in 

 i ph\ -iol. ,J. al condition generally. It i-s then that theph\-io- 

 . al continuity of the piece through the tran-itional middle 

 on miuht be -\ peeled to be especially afl'e. ted b\ li-rupti\e 

 leiideii. ies -i>iin:^in:< from the antagonism of proximal and di-tal 

 -\-lein- -o iib\iou-I\ antagonistic in the fi>-ioii -ho\\ n in 1 ig. 

 lo. In that case, the canals are complett l> obliterated at the 

 coii-trit -tion and the ti--ue is opaque and apparently impo\er- 

 i-hed. Thi- con-tricted region is under ten-ion, uhich probabh 

 accounts in part for its form. The ten-ion i- produced by the 

 acti\e migration of the l\\<> pol\ p- a\\a\ from each other, in the 

 manner of the oppo-ite hal\e- of an anemone in process of ti--i<.n 

 b\ rupture. 1 The initial di-coiitimiit\ i- thu- a< < entuated by the 

 acti\ itie- of the po|\ p- them-el\ 



Porrey, J 1'ubl. Zoo/., i ;. Ji i. 



