The nervous system in the Cestode Moniezia expansa. 379 



terior outer edge of the posterior lateral ganglion , passes outward 

 for a short distance, and then turning passes forward through about 

 three-fourths of the length of the proglottis ; but in no examples 

 that I have seen is it continuous through the whole of the proglottis, 

 as stated by Cohn (1897) for Taenia. In ray preparations the 

 branches of the marginal nerve are distributed to the margin of the 

 posterior three-fourths of the proglottis (PI. 23, Fig. 12), only a few 

 fibres indeed reaching as far forward as the anterior fourth. The fibres 

 from the short, posteriorly directed marginal nerve ennervate the 

 greater part of the margin of the anterior fourth of the next following 

 proglottis, but I was not able to find any branches that extended far 

 enough backward to meet the fibres of the long marginal nerve. It 

 is of course possible, in view of the great variability of the peripheral 

 nerves of the parasites, that there may be cases where the marginal 

 nerve is continuous and well-marked throughout the entire length of 

 the proglottis, but I have not yet seen such a case. The structure 

 of the marginal nerve is shown in PI. 22, Fig. 10. Nerve fibres are 

 given ofiP on all its sides and at frequent intervals, and there are 

 numerous, spindle-shaped ganglionic cells along its course. 



The two dorsal and two ventral nerves discovered by Niemiec in 

 the scolex and neck region of Taenia, are easily demonstrated in the 

 younger proglottides (PI. 21, Fig. 1), and in some cases, at least, 

 exist in the mature proglottides as well-defined nerves with the 

 elements closely gathered together. These, which I have described and 

 figured in an earlier paper, are also represented in the diagrammatic 

 Figs. 1 (PI. 21), 6, 7 (PI. 22), 12 and 13 (PL 23). It must not be sup- 

 posed, however, that these nerves always appear with the same diagram- 

 matic clearness, for it is only in exceptional cases that they are so well 

 defined. In the greater number of specimens examined these nerves 

 had become a loose, ill-defined band of tissue lying in the layer of the 

 longitudinal muscles, with which the nerve is closely associated. In 

 my earlier paper I have called these nerves dorsal and ventral con- 

 nectives, but I am now satisfied that they are continuous throughout 

 the entire length of the animal, and are therefore equivalent to the 

 four nerves of Niemiec. These nerves pass through, or are closely 

 associated with, the dorsal and ventral commissures of each proglottis. 

 At the place of crossing the two form a loose mass of nerve fibres 

 with an increased number of ganglionic cells. These crossings I have 

 previously designated as ganglia, and have named them according to 

 their position in the proglottis. I have continued that nomenclature in the 



