738 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [20] 



cases it does not represent a accessary condition of things. Some of the 

 individuals of var. (3 showed the same indistinctness with regard to the 

 occurrence of segments at the posterior end as is shown in Fig. 6 of var. 

 a. Indeed, as will be shown further on, the segmentation in this worm 

 is more apparent than real. 



In the following detailed description I have not attempted to keep 

 the varieties separate. The varieties themselves have been sufficiently 

 denned in the foregoing and in the figures. 



The head is small, sagittate in a marginal view, oblong in a lateral 

 view. Near the anterior end is a constriction. The part in front of 

 this constriction is short, projecting in a thick lip with rounded edges 

 and bluntly rounded in front, nearly circular or somewhat quadrangular 

 when viewed in front, but usually with a slight lateral emargi nation 

 corresponding to the faces of the bothria. The latter organs are two in 

 number, lateral, oblong, rather deeply hollowed out in the center with 

 moderately thin edges, free and slightly flaring at the posterior ends. 

 In most of the specimens of this lot the edges of the bothria are irreg- 

 ularly crimped or crenulate. A cross-section of the head shows that 

 the edges of the bothria are thin, so that a section made transversely 

 through the middle of the head resembles two crescents with their con- 

 vexities truncated and then applied to each other. The bothria in 

 most of the individuals (var. /?) extend to or beyond the posterior edge 

 of the first segment. In one it reached quite to the posterior edge of the 

 second segment. There is no neck. The central core of the head be- 

 comes gradually thicker aud broader until it merges into the first seg- 

 ment. A series of transverse sections carried on into the second seg- 

 ment shows the outer tissues sloughing off until a concentric ring is 

 formed which indicates the posterior part of the first segment where it 

 overlaps the anterior part of the second. 



The anterior part of the body is rather slender, and slightly flattened, 

 usually linear for a distance of 30 to 40 mm , then increasing in breadth 

 uniformly until the greatest breadth is attained, which is about the 

 middle of the total length. This breadth is maintained until near 

 the posterior end where the body becomes distinctly narrower. In some 

 the posterior end tapers to a blunt point. This is notably the case in 

 var. a. One specimen, No. 4 of table, p. 350, measuring G10 mm , was linear 

 for the first 50 mm . In the next 75 mm it increased in breadth gradually to 

 3.5 mm ; 60 mm farther on it had increased in breadth to 6 mm . This breadth 

 it maintained within varying limits to near the posterior end. In var. a 

 the breadth of the first part of the body increases slowly but uniformly. 

 At a distance of 25 or 30 mm it is l mm broad ; 45 lum from the head it is 

 2.5mm broad ; 100 mm from the head 5.5 mm broad. 



The segments which immediately follow the head are decidedly funnel- 

 form, the large posterior edge of each inclosing the narrow anterior end 

 of its successor. These in some cases are followed, in the anterior part 

 of the body, by segments with parallel lateral margins, aud with the 



