Fif:. 4.—Lii,eus ™-/»;/(/;«6-. -Coiitinuatioii of the series of diasrams illustratiu.i; the vascular system (solid 

 black). CM., circular muscles; Int., intestine; M., mouth: Oes., u'sophagus ; P.S., cavity of 

 proboscis-sheath. 



A— Bridges of connective tissue and muscles begin to cross tlie lilood-space irregularlv, breaking it up into a network 

 of intercommumcatuig vessels. A small blood-vessel, with verv thin dorsal wall, is now appearing in the wall 

 of the proboscis-sheath, on the ventral side. (The proboscis is no longer seen, having been torn out in this 

 specimen.) 



B— A median ventral blood-space has appeared temporarily, 

 tissue, and separated into two lateral spaces. 



C— The branches of the blood-space are becoming widelv separated, and spreading round to enilirace the walls of the 

 Lcsophagus and mouth, which have now appeared. 



D— The final condition of the blood-space with its network of vessels. Tliesc now lie below the inner laver of 

 lougitudnial muscles, and completely surround the intestine. The blood-vessel of the proboscis-sheath is 

 still seen, its dorsal wall l,eiiig an exceedingly thin incmbraue (exaggerated in thickness in the drawing). 



liut is already l)cing encroached upon by the connective 



