BIOLOGICAL STUDIES ON CORYMi >KI'HA. 299 



brought about by a knife- in Tnbularia leads promptly to regenera- 

 tion at the- wound, tin- f, n t suggests that Tnbularia develops \\ ith 

 .ter difticulty than Cormyorpha at the ligature because the 

 coenosarc recei\e- a -mailer supply of oxygen in that region. 



Tin- \ie\\ vi I by the following experiment, in \\hich 



the factor .if contact, which tends to inhibit development orally 

 in L'orytnnrpha, wa- eliminated. 



Fifteen .-h about 2 cm. lonu were cut from fifteen 



Tnbnlnria -tem- of -imilar size and condition, ju-t below the 

 hxdranth. The di-tal end of each wa- in-erted in a capillary 

 Vila-- tubi- . l.,-ed at one end by a para Hi in- pln^' into \\hich it 

 fitted easily, without terminal contact, nnill quan- 



tity : the proximal end \\a- free. A- a <i>ntrol, \<> 



-imilar pie< es were cut, both end- remaining i\> 



1 "rt\-h\c hoiir> later, the piece- in the tube- had de\elopeil 

 nine h\dranth- (tn the outer (proximal' end-, nothing \\ the 

 inner end-. In the control, though titteen ..f the -ixtecn pi. 



ed di-tal h\drainhs, no proximal Indranth- \\ere \i-ible. 



Twenty-five hours later still, all the pii-i e- in the tube- ji-- 



d pr"\imal hydranths; nothing had de\ eloped on the inner 



idi-tali end- In tin- control, only eiijit proximal h\dranth- 



\\eie present. 



l\iii'\ed now from t he tubi--, all the ]iie e- rapidl> prudmed 

 ii"i mal h\<lranths distally. 



Tin- experiment -eems to e>tabli.-h (l) that the failure >i<- 



lariii si : ninths, 'chcn ligatured, immediately /'. 



the ligature, is due to lack of oxygen; (2) that >i tin 



distal end in a 'Jass cap leads to the sa>> deration of 



'.ofncnt </ ///< proximal hydra nth as does the f)re f a 



ligature; and ; v i ///(;/ accordingly, sn<ii iicceleration is due to the 

 inhibit; the distal hydranth in the absence of 



an adequate supply of oxygen, rather than to an interruption of or 

 other change in the the circulation in the canals. The 



( in illation i- merely a transportation -v-tein, carrying -nbstances 

 fa\i'iiii- de\elopment that are rcinoxed from the -tie. mi by those 

 tissues e-pecially that have I: 6SS to ox\-gen, that i-, b\' the 



tissues al the open ends of the peri-arcal t ube. The po ibility 

 that oxygen mi-ht |ila\ -nch a role in thi- pn.ce of selection 



