Japanese Tricladida Maricola. 



23 



nt 



the innermost nerve iV^, so that the definite distinction could not 

 be demonstrated with any satisfaction to myself, there exists the 

 fine anterior longitudinal trunk 

 which is continuous with the pos- 

 terior trunk. Those of both sides 

 are connected together by three 

 fine transverse commissures in 

 the brain region. Anterior to 

 these there are present at least 

 four transverse commissures be- 

 tween the trunks. Lateral nerves 

 are given off from the points of 

 insertion of the commissures in 

 the longitudinal trunk, and pro- 

 ceed, without branching, to the 



body-margin, where they join the 



marginal nerve plexus. 



The dorsal nervous system 



seems to have in the brain region 



the same appearance as in Fr. 



ulvae. However, nothing more 



than three lateral nerves could be 



brought under observation. 



^t. trigonocephala (Text fig. 



2). The material of this species 



is in a state unfit for close study, 



hence I will limit myself to a 



general appearance of the brain. 



The brain lies fairly far behind the 



anterior body-margin, unlike the 



other forms, and has the same 



appearance as in the preceding 



species. The right and left halves 



of the brain are connected by 



three strong commissures. Each 



brain mass gives rise to at least 



7/2- 



m — 1- 



9n 



rs-- 



vd 



Text li<;-. 2. Sttimmeria trigonocephala. 

 Diagrammatic representation of the orga- 

 nization of an entire worm, as seen from 

 th dorsal side. 



Index letters as in text tig. 1. 



