xn. B. 4 Hilario arid Wharton: Echinostoma ilocanum 209 



crons long by 10 microns wide at the base. Then there is 

 another type of a shorter, thicker form, 44 by 18 microns, and 

 still smaller forms found in the corner groups and in the dorsal 

 row, which average about 29 by 15 microns. 



In those specimens where this wreath is not present no indica- 

 tion of such a structure can be seen, so it is not surprising that 

 it was overlooked by Garrison. A drawing of a specimen with- 

 out the spines is shown in Plate I, fig. 2. 



Ventral sucker. — The ventral sucker is the most prominent 

 feature of the surface of the body, the average size of this organ 

 in 6 specimens being 530 microns in diameter. The center of 

 the sucker lies at about the middle of the anterior third of the 

 body. 



Alimentary tract. — The oral sucker measures 120 to 200 mi- 

 crons in diameter and is slightly subterminal in position. It 

 opens into a short prepharynx. The pharynx is globular in 

 contracted specimens and has an average diameter of about 160 

 microns. In those specimens in which the head region is ex- 

 tended, the pharjTix is considerably longer and decreases slightly 

 in transverse diameter. The oesophagus is short (50 to 120 mi- 

 crons) ; it bifurcates just in front of the genital pores. The two 

 unbranched intestinal caeca pass transversely outward to near 

 the margins and then run posteriorly almost to the end of the 

 body in the marginal region. In the posterior part of the body 

 they are almost surrounded by the vitelline glands. 



Excretory system. — The excretory pore is in the middle of the 

 posterior border and opens into a large median excretory tube 

 which runs forward to the posterior border of the posterior 

 testicle, where it divides into two branches which run forward 

 between the intestinal caeca and the reproductive organs. Thus 

 they divide the body into three distinct regions, two lateral ones 

 which contain the intestinal caeca and the vitelline glands and a 

 median region containing the genital organs. In the region of 

 the ventral sucker the tubes increase in diameter and appear to 

 unite dorsad to the sucker. 



Male genital organs. — The testes lie in the posterior half of 

 the middle region of the body, one behind the other. In some 

 specimens they are oval and appear as solid masses, but generally 

 they are elongated and are distinctly divided into anterior and 

 posterior lobes by a transverse constriction. From each testicle 

 a vas deferens runs forward near the margin of the genital 

 region. They unite dorsad to the posterior sucker and enter the 

 posterior end of the cirrus pouch. The opening of the cirrus 



