296 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



Body. Slender and but slightly flattened ; head somewhat wider than 

 adjacent portion of body, with two pairs of oblique grooves of which the 

 posterior pair lies adjacent to brain; crescent-shaped rhabdites present in 

 integument, usually yellow, red, or brown in color. 



Size. Individuals of all sizes from very young worms less than 1 mm 

 in length to those mature forms that exceed 40 mm are frequently ob- 

 tained. Dwarf individuals rarely exceed 20 mm in length when sexually 

 mature, while an occasional individual of the large green variety may 

 reach a length of 80 mm ; diameter, 1 to 2 mm. 



Proboscis. Sheath extends entire length of body; proboscis armed with 

 slender, sharply pointed stylet and large cylindrical basis about 4 times as 

 long as its diameter and usually lj^-2 times the length of stylet. Basis 

 often, but not invariably, with lobulated posterior end (Fig. 39, a and e). 

 Each of the 2 lateral pouches usually contains 3 stylets. There are 10 

 or 1 1 proboscidial nerves. 



Ocelli. The youngest individuals, less than 1 mm in length, have only 

 4 ocelli, arranged as in T etrastemma ; additional ocelli appear later both 

 on the head and along the nerve cords back of the brain until a total of 

 100 or more may be found on each side of head and body (Fig. 39). 

 More than 30 of these may lie beside each nerve cord. There are 2 

 irregular double or triple rows anterior to the brain and a single irregular 

 row posteriorly. The eyes of reddish brown individuals are usually red or 

 violet instead of the usual black or brown. 



Color. Young individuals are milky white; older individuals are 

 tinged with yellow, pale yellow, pink, orange, pale brown, reddish brown, 

 golden brown, greenish brown or dark olive green, and occasionally 

 brick red. The colors are to some extent correlated with the environment, 

 although the pigmentation becomes intensified with age. Brown individu- 

 als often become green when placed in formalin; they also change to 

 white or bluish green after long confinement in the aquarium, because of 

 the disappearance of the more superficial pigment granules and colored 

 rhabdites which in life often mask the underlying green pigment. 



Habitat. Beneath stones and among algae, mussels, and other growths 

 on rocks and piers near low-water mark and below. This is the commonest 

 species of nemertean in many situations. The reddish brown variety is 

 most commonly found among corallines exposed to the full force of the 

 surf. 



Distribution. Coast of New England; British Columbia, Puget 

 Sound, Monterey Bay, and southward at least as far as Ensenada, Mex- 

 ico. 



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