814 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [96] 



mens and these which were obtained on this side of the Atlantic, I add 

 the following data: 



The head at rest is somewhat rectangular in outline. The bothria, 

 four in number, are opposite, that is, not arranged in marginal pairs, 

 oblong, rather bluntly rounded posteriorly, hollowed out on the face, 

 boat-shaped. They are divided into three loculi by two transverse 

 costa3. The two posterior loculi are of nearly equal length and shorter 

 than the anterior one. At the anterior end each bothrium bears four 

 simple hooks. These are in pairs, a pair near each margin. The bases 

 of the hooks in each pair are closely articulated, but do not spring from 

 a common base. The hooks are relatively long and slender, pointing 

 backward. They curve outward slightly at first, but near the points 

 return until they are nearly parallel with the axis of the head. The 

 outer hook of each pair (outer with reference to bothrium) is a little 

 longer and more slender thau its mate. The inner hooks have very 

 broad subcutaneous basal supports ; a prolongation of each approaches 

 that of the other and almost meets it. There seems, indeed, to be a small 

 solid piece which fills up the interval between the bases. Muscular 

 fibers can be traced to the basal supports of all the hooks. The hooks 

 themselves when magnified are seen to be hollow and filled with finely 

 granular material. The combined effect of these hooks is to form a 

 crown of sixteen hooks. 



In front of the hooks each bothrium is surmounted by a triangular 

 pad which bears a single supplemental disk. This part of the bothrium 

 is capable of considerable variation iu shape. I have seen it approach 

 the trefoil shape figured by Van Beueden, but have never seen it assume 

 that shape definitely. 



The posterior ends of the bothria are free and are susceptible of much 

 variety of motion. In progressive movements the bothria are thrust 

 forward either by diagonally opposite pairs, by adjacent pairs, or singly. 

 When a specimen was placed under a compressor and slight pressure 

 applied a bothrium was pushed forward in front of the head and at- 

 tached to the cover-glass by the supplemental disk aud the posterior 

 loculus. By this means the head was dragged forward. The last part 

 to detach itself from the cover-glass was the posterior loculus, which 

 was acting as an independent sucking-disk. In ordinary progression 

 the entire face of the bothrium is attached to the supporting surface. 

 The head of the living worm is almost transparent. The bothria are 

 strengthened by bands of muscle fibers, which lie near the margins at 

 the bottom of the trough-like face aud send up short branches to the 

 upper edge or rim. Each bothrium is further strengthened by two trans- 

 verse muscular bands, which form the characteristic costa3. A single 

 bothrium in the living worm suggests a wire flower basket. When the 

 posterior ends of the bothria are reflexed they are seen to be joined to 

 the head by a broad membrane, in which lie bands of muscular fibers. 

 When the bothria are reflexed sufficiently, that is, when their posterior 



