ABNORMALITIES IN CESTODE MONIEZIA. 153 



may be due not to age or external conditions but to an individual 

 peculiarity. Some may feel inclined to regard this as a reversion 

 to an ancestral condition in which the division of the body into 

 regions of localized growth was less distinct and regular. 



($) Abnormalities in the Structure of Proglottids. 



Very closely correlated with the variations in form of the 

 proglottids are variations in the structure and arrangement of the 

 reproductive organs. This close correlation was pointed out in 

 detail in all those cases cited in Parts I. and II., in which the 

 reproductive organs were developed. Some points of interest 

 remain to be considered. 



The relative position in the proglottid of the various parts of 

 the. reproductive organs was noted in Part I. Each portion has 

 a more or less definite relation to the others and to the proglottid 

 as a whole. We might expect that a change in the form of the 

 proglottid would be accompanied either by a modification in the 

 form or arrangement of some part or parts of the reproductive 

 organs, or else, in cases of more extreme variation, that some 

 portions or all of the reproductive organs would be absent. As 

 a matter of fact both of these possibilities are represented. 



Considering first the modifications in form and arrangement of 

 the organs without loss of essential pails, we find that consider- 

 able departures from the form may occur without apparently in- 

 terfering with the function of the organs. Two sets of organs 

 may open through a single pore (Figs. 1 1, 22, a, b, Pt. I.; Figs. 

 36, b, c, 37, b, c, Pt. II.). In such cases the direction of the 

 ducts in at least one of the sets of organs is distinctly different 

 from the normal direction, being more oblique. In other cases 

 the ducts may run very obliquely toward the margin but without 

 uniting with others (Fig. 33, c' , d' \ Fig. 39, a', Pt. II.). In 

 cases of this kind the ducts may be and usually are much longer 

 than the normal ducts. In other cases the organs may be nearer 

 the margin than normally and the ducts are then shorter than 

 normal. The vas deferens may open directly into the seminal 

 receptacle as in Fig. 21, c' (Pt. I.), or two vasa deferentia or two 

 oviducts may unite (Figs. 21, a', 40, 41). 



Reduction in size of the female organs and reduction in the 



