FH:. ?i.Linrnx i-in-riiijiiiiiK. Diagrams of a series of transverse sections, illustrating the \nsmlar system, 

 which has been represented in solid black. The brain and nervous structures are hatched. 

 Pi',, proboscis ; P.S., cavity of proboscis-sheath ; /?., rhynchod;cum, seen opening to the exterior 

 in the first diagram (A). 



A Shows the median blood-siuus in the snout, lying dorgally to the proboscis-pore (fl.). Blood-sinus represented 



in solid black. 



B The proboscis-pore has passed into the rhynchodfflum (/?,), and the blood-sinus is of wider calibre. 

 C The blood-sinus becomes divided into two by a partition of connective tissue developing on tin/ dorsal side. 

 D There is now a complete wall of conuecti\c and muscular tissue dividing the two blood-spaces, anil enclosing the 



rhynchoda'iini. 

 E Nerves from the anterior part of the brain are appearing laterally, ami I he cent ral t i--iie i, encroaching more and 



more upon the blood-space-, so as to reduce them in si/c. 

 F The central muscular tissue begins to show spare.-, the beginning <>l tin- cavity of the probo-cis-sheath (P.S.). 



Blood-spaces still further reduced. 

 G The cavity of the proboscis-sheath is now seen completely surrounding the proboscis (Pr,), and -epa rated by a thin 



wall from the blood-space on cither side. The blood-apaces are pre^seil lii<tween the brain and the proboseis- 



sheath. so as to lie MTV narrow at this point. 

 H The blood-spaces have coalesced ventnilly, so as to form ;i T-shaped vessel encloMng the proboscis-sheath. 



