194 



COE 



Size. — Length 100—150 mm. In extension ; width 2 mm. or more. 



Ocelli. — Apparently wanting, although some irregular masses of 

 reddish brown pigment on the sides of the head may perhaps be con- 

 cerned with light perception. 



Proboscis. — The pair of proboscis nerves lying internal to the 

 circular muscular layer are remarkably conspicuous. Inner longitu- 

 dinal muscular layer almost completely wanting ; consequently the 

 pair of nerv^es appear to lie directly beneath the inner epithelial layer. 

 Fibrous crosses between the internal and external muscular layers are 

 very inconspicuous, although they are sometimes indicated. In many 

 respects, therefore, the structure of proboscis approaches the condition 

 found in Tceniosoma. Proboscis is attached posteriorly at the bound- 

 ary of esophageal and intestinal regions by a broad and powerful 

 muscle to the dorsal wall of the proboscis sheath. Posteriorly to this 

 point the cavity of the sheath is very small, and does not extend very 

 far back into the intestinal region. 



Vascular System. — A very large and extensive unpaired blood 

 lacuna is situated in the head in front of the brain, and completely 

 surrounds the walls of the rhynchodaeum, except on the ventral side. 

 Just in front of the brain the lacuna becomes broken up into smaller 

 spaces, which unite about the cerebral sense organs into a single exten- 

 sive lacuna on each side. These two large spaces are separated only 

 by a thin strand of tissue. Back of the mouth each sends off a series 

 of large anastomosing blood spaces aroimd the lateral and ventral 

 walls of the esophagus. These esophageal lacunse extend back nearly 

 two-fifths of the length of the esophageal region, where they unite 

 again with the lateral vessels, which have continued in the angle 

 between the proboscis sheath and esophagus. 



Nephridia. — The nephridial system is very short and is limited to 

 the second fifth of esophageal region. It is remarkable for the small 

 number and comparatively large size of its branches. The anterior 

 branches lie on the outer walls of the esophageal blood lacunae, while 

 the main longitudinal canal on each side lies above the esophagus and 

 ventral to the large lateral blood lacuna. After extending backward 

 for a distance of about 0.3 mm. (In an individual 100 mm. long) the 

 branches in the esophageal lacunae join the main nephridial trunk 

 which passes to the dorsal wall of the lateral blood lacuna. The blood 

 Yessels around esophagus extend posteriorly only as far as the most 

 posterior of these branches. The main nephridial trunk on each side 

 then becomes situated in the connective tissue just above the lacuna and 

 extends backward in this position, and without branching, for a dis- 



