750 DESCRIPTION OF BOTHRIOCEPHALUS LIGULOIDES. 



* 



between these strands, is often caused to sink in on either side by the 

 action of dehydrating fluids. To the longitudinal furrow of variable 

 length which thus results, Cobbold has erroneously attached too much 

 importance. Similar, usually smaller, furrows are not unfrequently 

 formed, as Cobbold has also figured, on the outer side of the muscle- 

 strands. On the broad anterior end of my specimens there were a 

 number of longitudinal furrows, which, as was shown by examination 

 of similar stages in other species (I was unwilling to sacrifice my single 

 specimen of Sparganum from the human subject), were associated with 

 the muscle-bundles into a number of stronger strands, serving apparently 

 for the retraction of the head (Fig. 390, A ). While these muscle-bundles 

 extend within the parenchyma for a long distance without special 

 change, they exhibit on the surface of the worm, below the usual cuticle, 

 a marked deviation, repeatedly dividing, ramifying, and reuniting to 

 form a more or less regular plexus, the strands of which often pursue 

 a transverse course, and thus replace the otherwise absent circular 

 muscles. With these strong bundles numerous isolated fibres are 

 associated, which branch off from the former, dividing here and there, 

 and penetrating the clear parenchyma at intervals in all three dimen- 

 sions of space. By their fineness and isolated course they recall the 

 sagittal fibres in the muscular layer of the Tccnicc, except that they 

 extend not only dorso-ventrally, but also transversely and longi- 

 tudinally. 



In contrast to the generally weakly developed musculature, the 

 vascular apparatus attains considerable development. In investigating 

 preserved specimens of Bothriocephalus lotus and B. cordatus traces of 

 the excretory system are only occasionally seen ; in this worm, how- 

 ever, a section cannot be made in any direction without exhibiting 

 numerous vessels of considerable calibre. In transverse sections alone 

 some thirty can be counted without difficulty. They are, of course, 

 especially sections of longitudinal vessels, which are, as is well known, 

 much more abundant in the Bothriocephalidse than in the Trcniadae, 

 and which penetrate the parenchyma of the body superficially as well 

 as deeply. They seem to be specially developed near the nerve cords 

 and the adjacent longitudinal muscle-strands. It is not, however, 

 merely in the number of longitudinal vessels that the vascular system 

 of this worm recalls that of Bothriocephalus, but also in the splitting 

 and anastomosis by which a distinct network is formed, with meshes 

 of considerable but variable width, and usually of rhombic form. The 

 vessels have no special external walls ; their boundaries are formed 

 by the common ground substance, so that they are to be considered 

 merely as lacunar passages. In spite of this, the fine muscular fibres 

 are not unfrequently disposed in a distinctly developed annular 



