4(14 



ZOOLOGY 



SECT 



gmove. There is a vascular system with dorsal and ventral longitudinal vessels. 

 iu each segment is a pair of simple nephridia. In Protodrilus there are two 



Br 



An ci- 



V. 



FII.. 36S. Trochosphere of Polygordius neapolitanus A, lateral view of entire larva ; 

 B, diagrammatic vertical section ; <?, transverse section through the plane nb in B ; An. anus ; 

 An. (/. anal cilia ; Bl. blastocoele ; Br, apical plate ; Eat. enteron ; Msi!. mesoderm ; Ms<J. 

 li'i. mesoclermal bands ; Nph, head-kidney ; Oc, eye-spot ; Pr. or. ci. cilia of prototroch ; Prc. 

 iiin. proctodeeum ; Ft. or. ci. post-oral cilia ; St. dm. stomodseum ; ]'. Nr. C<3. ventral nerve cord. 

 (From Parkers Biology, partly after Fraipont.) 



Mtd (Sam} 



V.NrCd 

 Pr.a.n.ci. 

 An.ci 



stages : 



.. i.i'J.1 J_" l "I fili \S\J Ol/tltiV.O iil UAAV 



development 01 the somatic mesoderm ; fit I. coelome ; cat. Epiltm. coelomic epithelium Der 

 Spthm. Aerie epithelium; J/.j>/. muscle plate; M*<i. (.w,.), somatic mesoderm- Msd '(spl) 

 splanchnic mesoderm; 0. eye; t. tentacle. Other letters as in preceding fie-ure rProm 



1'^rkcr's liinlniiii, partly after Fraip'.i.t. ) 



ventral nerve-cords, connected together by transverse commissures : in Polygor- 

 dius the cord (Fig. 367, T'. Xt\ erf) is single ; in neither genus is there any trace 



