[9] ENTOZOA OF MARINE FISHES OF NEW ENGLAND. 461 



tractile. When the living specimen was viewed from the apex the aper- 

 ture (os) could be seen surrounded by many radiating lines like the radiat- 

 ing muscles of the iris. Iu a side view of a mounted specimen a globular 

 body about 0.2 mm in diameter can be seen lying in the center of the probos- 

 cis and about 0.1 mm from the apex. This globular mass has an aperture 

 which lies opposite the aperture of the proboscis. It probably repre- 

 sents the true apex of the myzorhynchus retracted. The head behind 

 the bothria is elongated into a neck -like part, which joins the true neck 

 or joiutless portion of the body by a definite articulation, which bears a 

 faint resemblance to a ball-and-socket joint, in which the anterior part 

 of the neck represents the "ball." There is also a difference in tissue, 

 the neck having, besides longitudinal fibers, transverse fibers and many 

 granular cells, while the neck-like portion of the head appears to be 

 composed almost entirely of fibrous tissue arranged longitudinally. 



In the other type the pedicels of the bothria are inflated and some- 

 what globose; the thickened border of the disk is not so much folded 

 as in the first. The head behind the bothria is short and turgid. These 

 differences, although striking when extreme cases are considered, are 

 none of them so profound but that they may be accounted for by sup- 

 posing them to represent different degrees of contraction. The bothria 

 in the living worm are susceptible of great variety of form. 



The segments begin from 1 to 2 tom back of the head. At first they 

 are much broader than long, subsequently they become quadrate, then 

 longer than broad. As the segments begin to mature they show a 

 tendency to become narrowed anteriorly, with convex margins. A few 

 of the extreme posterior segments are four times as long as broad, ob- 

 tuse-pointed in front, posteriorly attenuate, with a truncate termination. 

 The genital apertures are marginal, opening a little behind the middle. 

 In some they are not exactly on the margin, but may be seen, in a lat- 

 eral view, to be situated near the margin and running obliquely toward 

 the center of the segment. The penis was retracted in all the specimens 

 examined. It could be seen lying coiled up in the angle formed by the 

 vagina where the latter turns abruptly from the middle of the segment 

 towards the margin. The vagina could be traced from the ovaries in 

 the posterior part of the segment along the median line until it reaches 

 a point nearly opposite the marginal opening, where it turns abruptly 

 towards the margin and opens immediately in front of the penis. The 

 vas deferens is represented by a convoluted mass of tubes in the center 

 of the segment. The anterior part of the segment is filled with large 

 globular masses (ova). These are surrounded by a thick transparent 

 membrane, and have a granular interior. A layer of oblong granular 

 masses, smaller than the interior globular masses, surrounds the latter. 

 This layer is adjacent to the marginal wall of the segment and the 

 masses are at right angles to it. 



In some specimens the median and posterior segments are very irreg- 

 ular in shape. This irregularity is sometimes produced by the appar- 



