ON THE CAUSE OF AUTOTOMV IN TUBULARIA. 39 I 



traction in response to stimulation therefore seems to be the ef 

 muse of antotnmy. 



It ha- lieen po iMe in a few instances to ;^et a beautiful demon- 

 :iion of tin- -tn-n-ih of the contraction in the "neck" re-ion. 

 It .1 i iilmlarian In- found with the gastro- vascular cavity of the 

 hydranth well expanded and full, it fan sometime- 1 >e induced 

 I)V prii -knitf the peri-toim to contract tin- peri-tome lir-t . and 

 thu- retain the \\ hole of the tin id of the cavity. In this condition 

 the hvdranth -omewhat re-eml>!e- a ruM>er hall: ihe channel to 

 the ont-ide In-ill- c!o-ed 1 ,y the c. MI i meted peri-tome, and the 

 po-ti-rior < 01 mm i.t tion with tin- ca\ ity of the -tern or l>od\ U-in- 

 interrupted 1>\ the above-mentioned coniraction of the "neck" 

 on It iiou . \\iih an appropriate Mum instrument, piv ure 

 l><- liroii-lii lo IPIMI- upon tin- ^phere. and the u hole |nc,, .-cdin- 

 earrii-d out iindii the I >inn< ular. one <MII \\ at ch e\ er\ t hin- and 

 gauge \\ith one's "\MI mu-cle- the -tren-th of the coniraciion 

 in the peri-tonn- and "ii<-ck." In the in-tame- \\hen- I ha\e 

 < arrii-d m ihi- experiment / //<KT n< >n iihlc tn force the 



<>/><>! />i\' ni tin- t humid in the nc< k re-jinn. Some part of the 

 h\ pOStOme \\all i- t he tir-t to break. 



It is, too, this ven strong contraction thai carrie- the caenosarc 



ot the ;/, <>n (|iiite a\\a\ from the peri-arc see I ig. o). 



l'io|iaM\- tin 'ii that the point <.) the autilom\ i- al\\.i\- 



!elinitel\ loc.ili/ed in tin- "neik" re-ion as ua- tir-t re< 

 ni/e<l \>\ i .iard is that tin- remainder of the -lender portion of 

 the animal i- i o\ ered uith a chitiiioii- peri-arc \\hich i- r.ither 

 impermeaMe and hi'^hK pn>tecii\e a^ain-i -timuli. 



In "normal" cases ihi>-e in \\hich the process <\ aniotmiu' 



xtended over a period o| several hour- or ,1 |,i\ or t \\ o it 

 i- \\ell knoun that a \ei\ complete histolysis of the cell- iii the 

 "neck" re-ioll OCCUrS. I'llele i- gOOd e\ idelice lloU e\ er that 



ill the-i cases, i"". the hi-iol\-i- i- preceded l>y a rather strong 

 or 1>\ a prolonged ci>ntra< lion of thi^ region. In \ er\ \\eak -olu- 

 tion- of tellurium and -eleiiium -alt-, ot acid- and alkali-, and 

 e\eii |i\ \\atchtnl mechanical stimulation of the animal into 

 coiilimioll-l\ coiltrai led -late. I ha\e lieen aMe to effect I he 



Giard, \ . "I.'Aui"t"iiii.' il.in aiiinmlf." R ';//'//.. p. 



