THE FREE-LIVING FLATWORMS (TURBELLARIA) 



345 



49 (48) Each spine consists of two joints. Stalk much reduced and variable 

 in shape Dalyellia articidata von Grafi igii. 



Similar to D. rheesi in color and general structure. Sexual organs differ as shown by a com- 

 parison of Figs. 610 and 611. Same localities as D. rheesi. 



St 



Fig. 611. Dalyellia articulata. [A) Posterior end with sex organs from a strongly compressed specimen: 

 be, bursa copulatrix; ch, chitinous part of male organs; ge, ovary; gii, genital pore; rs, receptaculura 

 seminis; «, uterus with egg; vii yolk gland; vs, vesicula seminalis. {B) Chitinous organ with the reduced 

 stalk (5/). (C) Chitinous portion of cirrus showing variation from (5). Much enlarged. (After von Graff.) 



50 (47) The reduced spines on the terminal branch are unjointed and consist 



of but one piece 51 



51 (52) The dorsal transverse bar bears a row of fine spines. 



Dalyellia mohicana von Graff 191 1. 



Free swimming, of extremely slender form, similar to D. 

 rossi. Anterior end of the chitinous portion of cirrus not 

 sharply defined. Differs from D. rossi chiefly in structure 

 of the chitinous organ, the stalk of which is not so broad 

 or flat as in that form. One terminal branch of this organ 

 bears eleven curved teeth, the other seven of the same 

 type and one which is larger and three sided. The trans- 

 verse bar bears a row of straight, sharply pointed spines. 

 Brackish water, Falmouth, Mass. 



Fig. 612. Dalyellia mohicana. (/I) The animal swimmmg. 

 X 60. (B) Chitinous part of cirrus. Much enlarged, ca, end 

 branch with a row of spines; si, stalk; qd, dorsal transverse 

 connecting bar, with a row of spines, as; qv, ventral transverse 

 bar; mv, median projecting piece. (After von Graff.) 



