﻿SIPUNCULID WORMS OF CALIFORNIA — FISHER 425 



on the concave margin is frequently absent, while there is no uniformity 

 in the degree of curvature or in proportion of height to base. 



Plate 36, figure 4, shows the crown of 24 tentacles and nuchal organ, 

 which is relatively large in this species. 



Longitudinal muscle bands anastomose rather freelj", but there is 

 great irregularity in the extent in different specimens. The number 

 of bands between the origins of the anterior and posterior retractor 

 muscles varies from 20 to 25, but at the level of the nephridiopores is 

 15 to 17. In a form from Monterey Bay one or two very narrow 

 strands regularly split off from the principal bands (which are therefore 

 narrower than usual) and remain separate for considerable distances, 

 and are as much independent bundles as the principals. In such a 

 specimen the muscle count runs to 35 or even more. A short distance 

 in front of the anus the longitudinal muscles unite to form a con- 

 tinuous sheet. The introvert is ordinarily not invaginated beyond 

 this point, but can be retracted as far as the anus. In fully expanded 

 specimens the retractors are slender. The ventrals arise at the 

 beginning of the posterior third of the trunk from six or seven muscle 

 bands (first or second to sixth or seventh) but details of the relation 

 differ on the two sides and from specimen to specimen. The dorsals 

 arise from usually the fourth to sixth or seventh (or their equivalents 

 if there happens to be much anastomosis). Plate 39, figure 1, shows 

 the joining of the two retractors of each side to form one and the 

 ultimate fusion of these behind the head. There is a single fixing 

 muscle which shows little variation. It arises from two slender roots 

 on midventral line, in front of origins of the dorsal retractors, and is 

 attached by two distal branches to rectum and postesophageal gut 

 (pi. 39, fig. 1). The roots are attached to muscle bands 1-1 to left of 

 nerve cord. The spindle muscle begins just in front of the anus and 

 is attached at the posterior extremity. The contractile vessel is 

 inconspicuous. 



The nephridia are moderately long and attached for nearly their 

 length by a delicate mesentery. The small nephrostome is over the 

 interval between muscle bands 2 and 3. 



The nerve cord is loosely attached by its numerous nerves. There 

 are two eye spots on the brain. 



The gonad is in the usual place at the origin of the ventral retractors. 

 Ripe eggs are found in the coelom in February and March (Monterey 

 Bay). They are spherical and measure 0.12 mm. in diameter with 

 some as small as 0,1 mm. and others reaching 0.14 mm. In much 

 larger Humboldt Bay specimens coelomic eggs (January 1) have 

 the same dimensions. 



Type. — In the Museum of Comparative Zoology. 



Type locality. — Mendocino, Calif. 



