68 



especially the lateral fields, which may have 

 a breadth equal to the muscular cells. 



Excretory pore.— The excretory pore is 

 situated near to the middle of the esopha- 

 gus, at a distance of 1,044 to 1.0479 mm. 

 from the anterior extremity, and is the ter- 

 mination of a narrow canal directed from 

 within outward. 



Nerve ring. — This is situated at the an- 

 , terior part of the oesophagus, about 0,462 

 to 0,609 mm. from the anterior extremity. 



i4^0'/f//. -Subtriangular, protected by 

 three triangular lips, not very large and 

 each one showing two distinct papiillae. 

 The lips measure about 0,049 to 0,056 mm. 

 in length. 



Vestibule. Ample, comparable to that 

 of the Subulurinae; on section it is trilateral 

 or starshaped with three points and three 

 invaginations or angles (fig. 7). It is strongly 

 covered with chitin and the angles show 

 numerous small teeth directed inward which 

 increase in size from within outward (fig. 

 3). At the botton of the vestibule, guarding 

 the entrance to the esophagus, are three sub- 

 triangular prominences which are homolo- 

 gous to those existing at the bottom of the 

 buccal capsule of the Triodontophorns. The 

 vestibule measures 0,106 to 0,156 mm. in 

 depth. 



Esophagus. Constituted by the eso- 

 phagus properly speaking and by a volu- 

 minous subspherical bulb. The esophagus 

 properly speaking is rigid and subspherical, 

 and presents the last portion slightly dilated, 

 forming something like an outline of a se- 

 cond bulb, as seen in the Kothlanidae. The 

 walls of the esophagus are strongly mus- 

 cular, appearing to be formed of three 

 series of cells whose protoplasm is almost 

 entirely differentiated into radially disposed 

 muscular fibrillae. The cavity is very curious 

 and is trilateral on section, there being three 

 branches which start from a central portion 

 and widen outwards. This cavity is lined 

 by a strong chitinous cuticle, as can be seen 

 in figures 7 to 10, the central parts being 

 obliterated by a structureless substance, so 

 as to leave as free cavity only three ducts 



of semilunar transverse section (Fig. 8). 



These ducts fuse at the height of the 

 vestibule and near the terminal portion where 

 the obliterating substance of the central 

 portion becomes progressively reduced, and 

 the lateral diverticula diminish until reduced 

 to the form of a threepointed star, when 

 seen in transverse sections (fig. 9.). 



The esophagus properly speaking mea- 

 sures 1,044 to 1,914 mm. in length by 0,1 04 

 to 0,121 mm. in diameter. 



The bulb, which begins immediately after 

 the esophagus properly speaking, is sub- 

 spherical and has the same structure as the 

 esophagus, the internal lining being much 

 thicker, and differentiated into three strong, 

 chitinous valves with longitudinal grooves. 

 The diameter of the bulb is from 0,313 to 

 0,481 mm. (Fig. 10). 



Intestine. — Following on the esophageal 

 bulb is found the intestine, which, for con- 

 venience of «îtndy and on account of its 

 very complex structure, we will divide into 

 the following parts: 1) cecum; 2) first por- 

 tion; 3) midportion; 4) terminal portion; 5) 

 rectum. 



The cecum or intestinal diverticulum 

 (Fig. 9, 10 is a portion of the intestine 

 which is prolonged parallel to the esopha- 

 gus on the ventral side. This cecum, which 

 measures from 0,957 to 1,218 mm. in length, 

 is fingershaped, more or less cylindrical, 

 and has a pronounced flattening in the region 

 of the esophageal bulb to accomodate itself 

 between this organ and the body wall. The 

 structure of its walls is simple, of moderate 

 thickness, with ample cavity, as can be seen 

 in figure 9 and 10. 



The appearance of the walls of the in- 

 testinal diverticulum is similar to that obser- 

 ved in the midportion of the intestine. The 

 opening into the intestine is ample, the ce- 

 cum forming an intestinal prolongation with- 

 out sharp transition. 



The first part of the intestine follows on 

 the esophagus and intestinal diverticulum ; 

 it is the most voluminous part of the diges- 

 tive tube. The part in contact with the eso- 

 phageal bulb and with the beginning of the 



