344 



FRESH- WATER BIOLOGY 



46 (45) Each chitinous stalk bears a single terminal branch set with 

 spines 47 



47 (50) The spines on the terminal branch are jointed 48 



48 (49) Each spine consists of three joints. Stalk long, somewhat variable 

 in shape Dalyellia rheesi von Graff 1911. 



Length i mm. When swim- 

 ming freely the anterior end is 

 broadly rounded, in crawling, 

 truncated as shown in figure. 

 Integument colorless with riu- 

 m e r o u s delicate rhabdites. 

 Mesenchyma colored by sepia- 

 brown to cinnamon-red gran- 

 ules in a clear yellow fluid. In 

 the living animal the brain 

 region appears clear white and 

 the ventral surface lighter in 

 color than the dorsal, eyes 

 black. In pools along Erie 

 canal. 



FIG. 6 10. Dalyellia rheesi. (A) 

 slightly compressed: te, testes; vi, 

 yolk gland; vs, vesicula seminalis; 

 ch, chitinous portion of cirrus; dg, 

 duct of yolk gland; be, bursa copu- 

 latrix; go, genital pore; e, egg; ov, 

 ovary. X 60. (B) Male copuia- 

 tory apparatus: pr, cirrus tube; 

 meg, male genital canal; o, open- 

 ing of genital canal into common 

 atrium; st, short stalk of chitinous 

 piece. X 600. (C) Median ventral 

 grooved piece (mv) turned back; 

 st, variation in stalk. X6oo. (After 

 von Graff.) 



