TIIK SKICTI 1.AK1H.K. 



13 



trumpet-shaped in well-preserved -pecimen.-. lint I have not been able to \c-rify tliis observation: 

 :ui(l those specimens thai 1 have seen alive, aa S. jmmila &n<l S. co7*nicina, b&vd inv&ris,b\y had 



I nic conical proboM-ides like tho-e of the Plumularidse. I have also seen the expanded living 

 hydranth.s of Sertularetta pofyzonias and /'/,///</// ,//;/,/,/,</. and here, too. the prohosci- ua~ 



conical. 



Tin Hi/lira/ Ii, i;-i . All of the Sertularidse beliio- colonial forms die individuals, as already 

 indicated, are subordinate to the colony as a whole. None of tin- hydrothecae in this group are 



furnished with pedicels of any considerable length, 1 and the sessile condition has resulted in a 

 (rue bilateral symmetry that seems to be universal in this family and the Plumularidffi. The 



o m 



17 



THI BO-i CULAR HUSCLEE 



KlLT. 17. /'//./m.'Y.I i/M///.f//>. i, it, ..J,i'ivil]:i] !ni: . , 



i''rj. i - - ; , ilar muscle. 



l''i^'. ]'.'. >> '.'<!.~/::l/!'l. .1 /// , I l| .< Tl ' I ] lil P I 1 1 I 1 *<' 1 I ' . , ' < ' 1 f: !' ' I Mf I 1 1 1 ] *l "1 1 . 



Fig. -jd. iiyiir.i Hi. < a ,,[>,,/. [ntiathecal ridge at r, 



reason for this seems to be that the stems and brunches u|ion which the hydrothecffi are sessile 

 are in general more or less erect, or at leasl not horizontal in position. The normal posture of 



the hydranth is erect or nearly SO, the month beinn- directed upward. 



Hence the axis of the liydrotlieca forms an acute an^le with that of the stem or branch upon 

 which it gTOWS, and as a result the adcauline side tend.- to be shorter than the abcauline. Iii 

 other words the posture of the hydranth determines the inclination of the hydrotheca in the 

 Sertularida 1 . while the flexibility of the pedicel in the ( 'ampanulariihe permits (he hvdranth to 

 be directed upward without disturbing the radial symmetry of the hydrotheca. It thus comes 

 about that t he serf nlarian hvdrotheca lend- to assume a symmetry that is bilateral rather than 



1 If the .V,r//./,W/,; x,j;t,,i-;,i ili-srrilii-il in \}n~ \\,,i'k (see l'l;ite XX, li;.'s. 10. Ill is ii'lult. ;is sci-nis :ilti,..'etlier likely, 

 it wuiiM In- an ex.-ejititin to this -taleiiirnt, as the liyili'..llii'c,-i- in this spiviet have peilicels of c-oiisi.leralile leiiL'lh. 



