EXPLANATION OF THE PLATES. 449 



Fig. 15. The same, after the action of water. 

 ,, 16. A male Ancylostomum duodenale, of the natural size. 

 „ 17. The same, magnified, and seen laterally. 



a. The long single penis. 



b. Kegion of anus. 



c. Opening of the two organs of secretion. 



d. Lower broader portion of the organ of secretion, with a nucleus. 



e. The convolution of the cysts. 



,, 18. Female of Ancylostomum duodenale, of natural size. 

 „ 19. Lateral view of the same, largely magnified. 



a. Oral aperture. 



b. Anus. 



c. Opening of both organs of secretion. 



d. Vulva. 



„ 20. Lateral view of the upper part of the body of Ancylostomum duodenale. 



a. Lower portion of the ventral edge of the oral sucker. 



b. Upper portion of the edge of the sucker, towards the back. 



c. Muscular oesophagus. 



d. Intestine. 



e. Secretory organ of left side. 



f. Opening of the secretory organs on the ventral side of the worm. 

 ,, 21. Posterior view of the upper part of the body of the same worm. The dental 

 apparatus is seen through the oral aperture above. 



a, a. Lateral papilla;. 

 ,, 22. One of the four teeth from the oral aperture of the same worm. 

 „ 23. Anterior view of the same worm. 



a, Lower arch of the oral aperture. 



b, b. The lateral papillae. 



c, c. The two secretory organs. 



d, d. Their nuclei. 



e, Their openings. 



,, 24. Lateral view of the posterior extremity of a male Ancylostomum duodenale. 



a. The straight penis. 



b. Dorsal side. 



c. Ventral side. 



d. The middle single ray of the eleven parenchymatous rays projecting from 



the open caudal vesicle. 



e. Region of the anus. 



„ 25. Posterior view of the same. 



a. The right flap of the caudal vesicle. 



b. The middle single parenchymatous ray. 



,, 26. Male of O.vyuris vermicularis, magnified 230 times. 



a. Winglike appendage to the mouth of the worm. 



b. The pharynx, with club-shaped enlargement. 



c. The head of the gullet, with a peculiar valvular apparatus in its interim 



(a kind of gizzard). 



d. Stomach. 



e. e. Intestinal canal. 



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