180 ILLINOIS BIOLOGICAL MONOGRAPHS [468 



pseudoscolex. This latter statement applies in a greater degree to the struc- 

 ture shown in figure 34, since in it still more degeneration is present to the 

 extent that no traces of the radial fibres are to be seen altho there are very shal- 

 low bothrial depressions. In each case there appears in the medulla and among 

 the longitudinal muscles near the tip of the organ a considerable amount of a 

 material which takes the Orange-G counterstain very readily. While this is 

 relatively more abundant in the older of the two pseudoscohces in question 

 and intermingled with a good deal of calcareous material, it is confined more 

 lo the very tip of the younger organ. It represents possibly the first stages in 

 the development of the yellow homy material seen in the oldest and most degen- 

 erate pseudoscohces. 



Each of the chief nerve strands has a diameter of about 45jLi and is situated 

 usually dorsal to the cirrus and vagina, but occasionally ventral. Linstow 

 (1889:243) gave the diameter as 56//. Near the scolex of the youngest strobila 

 at hand it was found to be only about 34/i and traversed with transverse and 

 sagittal muscle fibres. Within the scolex the two strands gradually converge 

 and become united between the bothria by several weak and indistinct strands 

 in heu of a commissure. 



The excretory vessels are small and irregular in number and arrangement 

 in the mature segments. Lonnberg gave their number as 10 in young segments 

 and from 30 to 35 in mature proglottides, but anteriorly and in young strobilas, 

 there are two chief canals, as stated by Linstow, close within the nerve 

 strands, accompanied by several smaller ones. They break up in the pseudo- 

 scolex into an irregular plexus and posteriorly in the youngest strobilas empty 

 into the terminal vesicle, sho^Ti in figure 63. 



The first traces of the rudiments of the reproductive organs were seen 5.2mm. 

 from the anterior end of the smallest strobila found, which v/as 22mm. in 

 length. The genital cloacae alternate irregularly from side to side, altho they 

 may be situated on one side for stretches involving at least five proglottides. 

 Dujardin (1845:617) described them as being unilateral or very irregularly 

 alternating, while Linstow (1889:244) said they were one-sided, and between 

 the middle and hinder one-third of the edges of the proglottides. In the sec- 

 tions made they were found between the first and second thirds, often covered 

 by the edge of the proglottis next ahead and from 35 to 75m in depth. Since 

 the actual opening is usually closed by the longitudinal contraction of the 

 strobila, it is dif&cult to distingtiish it externally from grooves separating con- 

 secutive proglottides or other lateral grooves between irregular rugae. The 

 vagina opens immediately behind the cirrus and slightly ventral, there being 

 no distinct ductus hermaphroditicus. This corresponds with Lonnberg's and 

 Linton's finds, whereas Linstow said that it is opened ahead of the cirrus. 



The testes are arranged in two lateral fields between the nerve strands and 

 the uterus and ovary in the median Hne. and are strictly discontinuous, that is, 

 separated longitudinally into sets corresponding with the other genitaUa by the 

 transverse muscular septa between proglottides. Their average maximum 

 length, width and depth are, respectively, 40, 90 and 85/x, thus indicating 



