[15] ENTOZOA OF MARINE FISHES OF NEW ENGLAND. 467 



space, in the center of which is a granular elevation. The tips of the 

 horns of these crescents are sharp-pointed, and form a circle of eight 

 hooks, which surrounds the tip of the rostellum. When this rostellum 

 is viewed from the side, each crescent is seen to be the recurved ante- 

 rior border of an oblong or triangular trough-like plate. These four tri- 

 angular plates occupy much the same relative position with respect to 

 each other as the jaws in Echinus, and suggest the ' : lantern" of that 

 animal. This j>roboscis was observed in all of the smaller specimens 

 and in some of the half-grown ones, but had been lost by all of the 

 larger specimens. It seems to have but a feeble attachment to the head, 

 and became detached from several specimens while they were being 

 examined. The length of this rostellum in the half-grown specimens 

 was about the same as that found in the smaller specimens, viz, about 

 0.5 nim . 



In a series of transverse sections made of a head of one of the larger 

 specimens, it was noticed that there was a circular aperture in the sec- 

 tions of the anterior part of the head, which doubtless marks the place 

 where the fleshy pedicel of the rostellum was inserted. The primary 

 lobes of the bothria spring from a central muscular portion of the head 

 (Figs. 9, 10), and consist of fascicles of muscular fibers which extend 

 into the secondary and tertiary divisions. The crisped appearance 

 of the head is due to minute crimped or frilled divisions of the lobes, 

 and not to the crisping or curling of the free borders of the lobes, as in 

 P. lactuca Van Beneden. The solid, central part of the head which serves 

 as a support for the so-called bothria, is pointed auteriorly, where the 

 lobes, in transverse section, appear to radiate from a common point. 

 It is on this extremity of the head that the base of the rostellum is 

 situated. This central portion or core of the head increases in size 

 until at the base of the head it has the dimensions given in the meas- 

 urements as the thickness and width of the neck. A transverse section 

 of the basal part of the head or of the neck, in the smaller specimens, 

 is rhomboidal (Fig. 12). In the larger specimens the breadth of the 

 neck is greater in proportion to the thickness than is the case in the 

 smaller specimens. In Fig. 10 a transverse section is shown of the 

 head of an adult at about the anterior third. The central core of the 

 head at this point is quadrate, and but two of the vessels of the water- 

 vascular system appear. Sections made transversely through the 

 middle of the head show the central core to be oblong (Fig. 9); The 

 central part of such a section is a clear space with a few connective 

 tissue fibers and granular masses in it. Both fibers and granules be- 

 come more crowded in the vicinity of the longitudinal vessels which 

 are sharply defined in cross-section. A transverse vessel was observed 

 in a section through the head, which connected the two inner longi- 

 tudinal vessels. The central clear space is limited by a dense layer of 

 muscular and connective tissue fibers, which make a circular layer of 

 tissue that can be traced back into the neck where it becomes much 



