Fid. 17. Diagrammatic view of the 

 structure of Planaria (Dendro- 

 coelum) lactea. x 7. The body 

 has been cut across and a por- 

 tion removed. In the posterior 

 half the alimentary tract of the 

 left side is removed and the 

 uterus, penis, and muscular organ 

 sliced open horizontally. The 

 nervous system is represented by 

 black, and the yolk -glands by 

 dotted lines, br, Brain ; ey, eye 

 with lens and optic nerve ; go, 

 external genital aperture for both 

 male and female products ; gs, 

 genital atrium ; Ig, paired lateral 

 intestinal branch ; In, longitudinal 

 nerve ; ing, unpaired anterior 

 intestine, the branches of which 

 are cut off close to the main 

 stem ; mgr, eversible " muscuio- 

 glaudular organ " ; nc, nerve-cells 

 in the pharynx ; nn, lateral 

 nerve -twigs ; ns, nerve -sheath ; 

 ov, ovary ; ovd, oviduct ; pe, 

 the eversible penis, the corru- 

 gated inner white portion of 

 which is the apex ; ph, pharynx ; 

 phs, pharyngeal sheath ; pr, 

 " prostate " or granule -gland (re- 

 presented by dotted lines opening 

 into the penis) ; ps, penial sheath ; 

 te, testes ; to, tactile lobe of the 

 head; ut, " uterus " opening into 

 the genital atrium just above 

 mgr; vd, vasa deferentia ; vs, 

 vesicula seminalis ; yg, yolk- 

 glands ; yo, openings of the yolk- 

 ducts into the oviducts. 



