No. 5,] THE CESTODE MONIEZIA EXPANSA. 229 



obliquely in their segment, the ducts extending outward and 

 posteriorly toward the pore ; but these positions are, I believe, due 

 to the relations of the segments to each other. The fact must 

 be recognized that in segments of normal length a complete set 

 of organs capable of functioning tends to form, however abnormal 

 its position ; i.e., the parts are formed independently and tend to 

 unite in the normal manner. In this case the proximal portions 

 of the organs a' and b' are formed in their normal position with 

 respect to the furrows bounding the segment ventrally. The 

 edge of a b shows no dividing furrow, so that it might be expected 

 that a pore would appear at its middle. The furrows d and e 

 approach near the edge, however, and the existence of a certain 

 degree of " internal division " at the edge is probable. Thus two 

 pores are formed instead of one, but are separated by less than 

 the normal distance between pores of two successive segments. 

 Apparently the degree of separation between the two segments 

 at the edge is only slight, so that the edge is more or less like 

 that of a single segment, and the middle region is the pore- 

 forming region. But the two segments are sufficiently inde- 

 pendent to give rise to two pores instead of one common to 

 both ; and these two pores, it will be noticed, are equidistant 

 from the middle of the undivided edge of a b. But the pore 

 in b is far posterior to the ovary, etc., and in order that the two 

 may be connected the ducts must extend obliquely, as they do. 

 In a, on the other hand, the pore is directly lateral to the proxi- 

 mal portions, and thus the ducts are horizontal. 



The furrows between b and c extend almost to the edge, so 

 that conditions here approach very closely to the normal. The 

 organs c' in c are normally situated as if the furrow f were 

 complete. 



Two of the furrows on the dorsal surface are interrupted (g g} 

 and the two parts overlap slightly in each case. 



Figure 7J. 



The variation from the normal form shown here is almost 

 identical with that shown in Fig. 1 2, a and b, except that here the 

 two partial furrows bend anteriorly at the right. Both become 



