254 



HENRY L. OSI5ORN. 



cleared and mounted whole. The form of the body is less 

 spatulate than that of P. folium or P. patcllare, the neck is less 

 distinct. The total length of this specimen is 3.5 mm., its greatest 

 breadth is 1.4 mm., the ratio of breadth to length is thus 40 per 

 cent. In P. patcllare this ratio is 66 per cent., in P. spatula 

 (Odhner, '02) it is 48 per cent. The American form is thus less 

 broad than any reported old world form. There is considerable 

 variation in this respect in my material, some cases being de- 

 cidedly slender, in one mature specimen studied alive under some 

 compression and measured from the camera lucida drawing, the 

 length is 4.2 mm., the width 0.88 and the ratio of breadth to 

 length 20.9 per cent. This specimen is more than usually nar- 

 row, most having the broadened form of Figr. i. 



o o 



FIG. 3. Section at the genital pore, X about 120. 



There is no pharynx, the oesophagus is short, the intestines 

 branch well forward, and are very long, reaching to the extreme 

 posterior end of the body. The cells of the intestine are pro- 

 vided with very long cilia, as in P. patcllare ; they would probably 

 be very interesting subjects for histological study. In both P. 

 folium and P. patcllare the intestines are somewhat sacculated, 

 but here they are entirely simple. 



The excretory system is like that of P. folin in and P. patcllare 

 dorsal posterior terminal pore, a long ventrally located bladder 

 branching anteriorly on the level of the hinder boundary of the 

 ovary. Smaller vessels and flame cells like Fig. 5 of Sturgis, 

 '97, are recognizable in sections. 



The chief important internal differences between this species 

 and those previously known are in the reproductive system. The 



