i I.NTRAL NKRYOUS ^\>TKM IN PLANARIA. 



45 



nected as they appear in the figure; some nerve fibers may extend 

 aero-, the space between them. The nerves passing to the 

 auri< les appear in the section and the alimentary tract lies on 

 i IK- dorsal side. Posterior to this level the nervous system con- 

 sists of the two main nerve cords, each composed of a fiber tract 

 including -ome cells and surrounded by other- ami ^i\inu ri-e 

 to in -r\e- and commissures at various level-. 



III. TKRATOPHTHALMK Hi \i>-. 



( t i In.- \aiious types of teratophthalmic heads only iln>-e \\hich 

 -hou partial t'u>ion of the optic pigment cup- were examined 

 Thf form- \\ith unef|ual or unsymmetrical I-NC> lonstitutr a 

 (littt-rc-nt type of teratophthalmia and n-'|tiin-a niori- 

 in\c-ii^ation: moreover, the partial !ti>i<>M- ot ilir eyes 



9 



FIGS. c> 



lead thmui'li all possible stages to tin- -indr nirdian r\c o! tin- 

 ii-raioiiion>hic head. 



l ; i-uir (> >ho\\- tin- outline of the- body and the condition of 

 tin- eyes in >iu- of the teratophthalmic heads >erti<mcd. The 



