160 



PLATHELMINTUES 



2. PoLYCHCERUS Mark. Body biojul 

 eral caudal filaments: 1 species. 



d Hat with either one or sev- 



Fig. 255 Fig. 256 



Fig. 255 — Aphanostoma diversivolor 

 (von Graff). 1, statocyst ; 2, female 

 genital pore; 8, bursa serainalis; 4, 

 male genital pore. Fig. 256 — Poly- 

 chosrus caudatus (Mark). 1, testis; 

 2, mouth ; 3, ovary ; 4, female genital 

 pore ; 5, male genital pore. 



P. caudatus Mark (Fig. 256). 

 Body with parallel sides and a deep 

 notch in the hinder margin, from which 

 1 to 3 caudal filaments arise ; color red ; 

 length 4 mm. ; width 1.5 mm. : on stones 

 along the beach from Casco Bay to 

 Long Island Sound; often abundant; 

 movements sluggish. 



Subclass 2. CCELATA. 



Turbellarians with intestine: 3 



orders. 



Key to the orders of Coelata : 



Oi Small forms with a straight intes- 

 tine 1. RlIABDOCCELIDA 



«2 Usually larger forms with branched 

 intestine. 

 6i Intestine with 3 main branches. 



2. Tkicladida 

 62 Intestine with many large branches. 



3. POLYCLADIDA 



Order 1. RHABDOCCELIDA. (Fig. 257.) 



Marine, fresh-water, and land turbellarians of small 

 size in which the intestine is a straight and unbranched 

 or at the most only slightly lobed tube or sac; yolk 

 glands present or not; either 1 or 2 genital pores pres- 

 ent: 23 families, grouped in 2 suborders with over 350 

 species, of which about 75 have been found in this 

 country; about half the species marine. 



Key to the suborders of Rhahdocoelida : 



Ui Intestine a straight tube 1. Rhabdoccela 



flj Intestine sac-shaped with irregular sides. .2. Allceoccela 



Suborder 1. RHABDOCCELA.* 



Body cylindrical, fusiform, filiform, or lamellate in 

 shape; intestine a tube or sac, usually with straight 

 sides; usually 2 eyes and occasionally sense pits and 

 statocysts present; either a single median or a pair of 

 excretory canals present; many forms reproduce asexually, by terminal 

 budding: 16 families and 275 species, 48 American. 



• See "Monographie d. Turbellaricn, I. Rhabdocoelida," by L. von Graff, 1882. 



Fig. 257— Dia- 

 gram cf a rhab- 

 doccelid {Dalyel- 

 lia) (von Graff). 

 1, mouth; 2, 

 brain ; 3, intes- 

 tine; 4, yolk 

 gland ; 5, testis ; 

 fi. genital pore ; 

 7, ovary. 



