Some Variations in Hymcnolepis diniinuta 9 



or four altogether. In the anterior and also in the posterior re- 

 gions of each proglottid is found a ganglionic enlargement from 

 which arise two nerves, one running inward in the cortical por- 

 tion and one in the central portion of the parenchyma. In the 

 scolex the nerve trunks unite behind the rostellum in a commissure 

 richly supplied with nerve cells. From here arise four nerves 

 running forward on as many sides of the rostellum and contain- 

 ing nervous elements. These main structures are all I have made 

 out in my specimen. 



The subcuticular musculature consists here, as is usual in ces- 

 todes, of an outer layer of circularly running fibers and an inner 

 layer just internal, of longitudinal fibers. These are united into 

 minute bundles, between which the processes of the subcuticular 

 cells pass upward, to become continuous with the cuticula. 



The body musculature consists of longitudinal, transverse, and 

 dorsoventral fibers. The longitudinal are united into small bun- 

 dles of 8 to 15 fibers each. The bundles are arranged in two lay- 

 ers : the outer, just beneath the subcuticular cells, and arising 

 from subcuticular longitudinal bundles in the scolex and neck, 

 are the more numerous by far ; the inner are attached in the sco- 

 lex to the suckers and rostellum. In the worm under considera- 

 tion these two layers are so close together that they might readily 

 be mistaken for one, due to unusual muscular contraction of the 

 dorsoventral fibers. The transverse and dorsoventral fibers are 

 alike few in number, especially in the middle region of each pro- 

 glottid ; the latter are perhaps the more common. 



The two ventral canals are the most important of the excretory 

 system and run throughout the length of the strobila to the inner 

 side of the longitudinal nerves, sometimes with a lateral curve in 

 each proglottid. They are connected with each other by a trans- 

 verse canal having a slightly undulating course and somewhat 

 smaller diameter near the posterior margin in each proglottid. 

 Just above each of them is the corresponding dorsal canal, very 

 much smaller in diameter and only equal in size near the scolex, 

 where the ventral canal is found to be much smaller. The four 

 canals terminate in the vascular ring behind the rostellum in the 

 scolex. From this ring run forward four vessels, those on either 



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