PRELIMINARY DESCRIPTIONS OF SOME JAPANESE TRICLADS. 



161 



Color of body very variable. As seen on the dorsal side, full-grown 

 individuals are generally of an olive-brown color, sometimes but not always 

 with two darkish longitudinal bands running from behind eyes to posterior 



12 



13 



od gp 



12. Planaria gonocepltala in the creeping 

 state, about 4X- 



13. Same. Diagram of sexual organs. 

 Index letters as in woodcut 2. 



parts of body. Younger 

 individuals are paler and 

 the greater parts of body 

 may present various sorts 

 of hues — not unfrequently 

 reddish, brownish, yellowish 

 or greenish — according to 

 varying coloration of the 

 guts. 



Eyes two, lying slightly 

 in front of the line connect- 

 ing the apices of auricular 

 processes ; each lying in an oval colorless area. Besides the 

 usual pair, one or two adventitious eyes may sometimes occur. 

 Auricular sense organ slenderly reniform. 



Mouth situated at a point somewhat behind the middle of body or even 

 at about the commencement of posterior body third. Pharynx rather short. 

 Anterior gut trunk with 8-12 pairs of branches; each posterior gut trunk with 

 13-18 outer branches and about as many, but much shorter, inner branches. 



Genital aperture slightly in front of the middle of the posterior body 

 third. Atrium simple. Testes numerous, placed close together in dorsal 

 parts of body and arranged in two longitudinal zones which run from behind 

 ovaries to nearly the posterior end of body. Vasa deferentia entering the 

 bulbous end of penis separately and on the sides. Vesicula seminalis wide, 

 with more or less folded wall. Ejaculatory duct narrow, opening externally 

 on the underside of penis, not at the tip. In its course, the ejaculatory 

 duct shows an obliquely anteriorly directed annular outbulging ; it con- 

 sequently brings about a small, conical, posteriorly directed process which 

 projects into the said outbulging and which is axially traversed by a part 



