[25] NOTES ON ENTOZOA OF MARINE FISHES. 743 



toward each other where the thin lips of the bothria are cut through. 

 The bottom of the bothria cousists Of a layer about .03 mm thick of dense 

 transverse interlacing stria?. Along the sides the tissue is looser, with 

 open cellular spaces about .005 mm in diameter. There is here a more 

 definite arrangement of longitudinal fibers, which now lie in four masses, 

 one in each of the projecting corners of the quadrangular sections. 

 Each of these is at first somewhat circular with a clear central space, 

 a character which is presently lost. A narrow layer also lies along 

 the face of each bothrium immediately under the layer of transverse 

 tissue. Another mass lies opposite the middle of each of the shorter 

 sides of the section. The transverse fibers still predominate, however, 

 and even the masses of longitudinal fibers are quite abundant. 



Two large, irregular, clear spaces, crossed by a few transverse fibers 

 and filled with a granular substance, which is but slightly stained by the 

 carmine, indicate the continuation of what was seen in front of the 

 constriction. Besides these there are a number, at least four on a side, 

 of small spaces with definite outlines, which on account of their irreg- 

 ularity in contiguous sections are readily interpreted to be sections of 

 aquiferous vessels which pursue a spiral course. This was further 

 proved from longitudinal sections. Near the middle of the head a 

 transverse section has the appearance of two crescents pressed together 

 by their convex sides. The distance through the head from the bottom 

 of one bothrium to the bottom of the other is only .2 mm , while the oppo- 

 site diameter is .56 mm . Several vessels, as many as six on a side, were 

 counted beside the two large irregular, nervous (?) vessels. Each of the 

 latter is .054 by .032 mm in its two diameters, the longer diameter corre- 

 sponding to the longer diameter of the sections. At this point the longi- 

 tudinal fibers are pretty evenly distributed. Back of the middle tbe cen- 

 tral part of the head grows thicker and wider ; the margins, which at 

 first were gently concave and then strongly emarginate, assume a more 

 and more even outline, then bulge out into the rounded convex outlines 

 of the margins of the segments. The head is thus seen to pass imper- 

 ceptibly into the first segment. 



In some of the sections there were remains of what appeared to be a 

 dense layer of columnar epithelium lining the bothria. This layer was 

 still adherent to the inner edge of the thin lips of the bothria and ex- 

 tended nearly to the bottom of the pit. Becoming separated from the 

 underlying cuticular layer the detached portions break up into groups 

 of curved cells. The thickness of this layer, coinciding with the length 

 of the component cells, is .00§ mm . 



The sections which passed through the posterior parts of the bothria 

 also cut the posterior parts of the first segment. As the sections pro- 

 gress through this part, an outer concentric layer, about .09 mm thick 

 and containing radiating, transverse, and circular fibers, separates, 

 leaving a central oblong core, which contains the aquiferous and uerv- 



