Occasional Papers of the Museum of Zoology ii 



to the exterior. These vessels sometimes take on the appear- 

 ance of a broad Y with a short slender stem and broad thick 

 arms. From the anterior ends of the arms of the Y broad, 

 somewhat coiled tubes may be traced for a short distance an- 

 teriad where their outlines are lost in the parenchyma. 



Portions of the nervous system can be seen in some speci- 

 mens extending from the circumoesophageal commissure 

 toward the posterior part of the body, in a few cases as far 

 as the developing sexual organs. The cuticula is abouf 0.005 

 mm. thick and is unarmed with spines. ]Measurements of the 

 various structures are given in the accompanying table. 



^leasurements of Cercaria vcgrandis in millimeters. 



Average 

 Organ Type dimension Number Maximum ]\Iinimum 



of paratypes measured 

 Body length 0.273 



breadth 0.193 

 Oral sucker length 0.033 



breadth 0.030 

 Acetbulum length 0.023 



breadth 0.025 

 Pharynx length O.022 



breadth 0.008 



