''ormea from tl:e splarichnic me soder/aal linii:^ o :!" the trunk cav- 

 ity, ei^cloaes a part of the space betn'eeii ti:e liiiirit: and the 

 ■all of the all merit an/ cand; i.e. the s egmei.tatiori cavity; sec- 

 ond, that this vessel dv.'indles av/ay posteriorly aaid opens into 

 Liie space betweeii the linin^^ and the wall of the alimentary ca- 

 nal; third, that the v/all of tnn storaach in the collar se^^ment 

 is practically free from .'nesodeni.al linin.^ (Fi^-s, 51 (g)- (h) ) 

 ajid that the larval collar cavity with its soniatic iuesoderj.c:.l 

 lining is a blood sinus; ^burth, tha,t the larval collar cavity 

 is a part of the sei^meiit ati on cavity; and fifth, that durint: 

 irietairiorp!:osis the act of arawin-. the stomach and intestine into 

 the cavity of the veiitral pouch causes a pressure to be exertea 

 on the larv&l collar cavit;', 



T.'hen the critical s ta^e is beint. passed thj^ou-rh, the blood 

 corpuscle masses breaK up and tliey are driven by the pressure 

 on tr>e collar cavity to the points of lea3t retistance. As a 

 rule, some of the blood corpuscles are squee^iea up into L h.e dor- 

 sal rej.;ion of the collar cavity where t.ne aorsal blood vessel 

 -uds and invariably so ire o^ the blooa corpuscles pass from the 

 larvul collar cavity into tl^e cavity between the wall o *" tiie ali- 

 mentar-y cajrial and its mesodermal coverin,:. In fact, as soon 

 as the critical sta^^e occurs, the splanchnic mesodermal linin^^ 

 in all regions bf^comes separated ^"rom the wall of tir. alimentary 



