22 COE 



The main longitudinal muscular layer In most regions of the body 

 equals in thickness that of all the other muscular layers combined. 

 The lateral nerve cords lie imbedded in this layer. Internal to the 

 longitudinal muscles lies a small amount of gelatinous tissue or paren- 

 chyma of the body cavity. The inner circular muscular layer extends 

 from the mouth to the posterior end of the esophagal region. Its 

 fibers are continuous with those of the proboscis sheath. Anteriorly, 

 it is even thinner than the outer circular muscular layer, but towards 

 •the posterior end of the esophagal region it increases so greatly in 

 massiveness that for a short distance it exceeds in thickness the other 

 muscular layers combined. Having reached its maximum develop- 

 ment (near the efferent nephridial ducts), it suddenly disappears en- 

 tirely, its dorsal portion remaining for a few sections as a semicircular 

 arch above the proboscis sheath. 



Proboscis sheath. — This organ is more strongly developed than in 

 the other species of the genus, and possesses a single muscular layer 

 composed of circular fibers interlaced with longitudinal fibers in small 

 groups. 



Proboscis. — The anterior end of the proboscis is attached to the tis- 

 tues of the head at about the middle of the brain region. It walls con- 

 sist of a thin outer fibrous layer, on which rest the superficial flattened 

 epithelial cells bathed in the fluid of the rhynchoccel. Beneath is the 

 thick layer of longitudinal muscles comprising nearly the whole of the 

 musculature. Internal to these are a few scattered circular fibers, then 

 a thin basement membrane, and, finally, the internal layer of columnar 

 epithelial cells. This inner epithelium is composed of a simple layer 

 of very long and closely pressed cells, a portion of which contain rod- 

 like masses of secretion. Their nuclei are closely packed together 

 peripherally, and comprise several layers as is usual in much crowded 

 columnar cells. 



A pair of rather large nerves extend throughout the length of the 

 proboscis just internal to the circular muscular layer. These nerves 

 originate from the ventral commissure of the brain very much as in 

 Carinella. They arise from the anterior border of the commissure 

 near its origin from the ganglia, and pass dorsally to the point where 

 the proboscis is attached to the tissues of the head. They then enter 

 the proboscis, and take up lateral positions in its walls corresponding to 

 those of the lateral nerves in the walls of the body. 



Nephridia. — The condition of the nephridial system is in many 

 respects intermediate between that of C. patagonica and C. arrnatidi.^ 

 the mass of tubules constituting the so-called nephridial glands not ex- 



