i56 



COLLEGE ZOOLOGY 



Order i. Rhabdocoelida (Fig. 103). Small Turbellaria, 

 often microscopic, with simple unb ranched intestine. Examples: 

 Microstoma, in fresh water; Monoscelis and Monops, marine. 



Order 2. Tricladida (Fig. 99). Turbellaria with intestine 

 of three main branches — one median anterior branch (i 1 ) and two 



Fig. 103. Plan of structure 

 of a Rhabdoccelous Turbellarian. 

 be, bursa copulatrix ; en, brain ; 

 e, eye; g, germarium; i, intestine; 

 In, ventral nerve cord; m, mouth; 

 p\u pharynx; rs, seminal recep- 

 tacle ; .y, salivary gland ; /, testis ; 

 u, uterus containing an egg ; 

 v, shell gland; vs, seminal vesicle; 

 $ , penis ; $ $ , genital pore. 

 (From Lankester's Treatise, after 

 v. Graff.) 



Fig. 104. — Plan of structure 

 of a Polyclad Turbellarian. 

 D, branches of intestine; 

 G, brain; M.Go e , male genital 

 pore ; 0, mouth ; Od, oviduct ; 

 Ov, ova; T, vas deferens; V, va- 

 gina ; W.Go e , female genital 

 pore. (From Sedgwick, after 

 Quatrefages ) 



lateral posterior branches (i 2 , i 3 ) ; many lateral caeca arise from 

 the main branches. Examples: Planar ia (Fig. 98), Polyscelis, 

 and Dendroccelum (Fig. 98, 1) in fresh water; Bipalium in the 

 tropics living in moist earth, and accidentally introduced into 

 hothouses all over the world; Bdelloura, Gunda, and Poly- 

 choerus in the sea. 



