44 ILLINOIS BIOLOGICAL MONOGRAPHS [394 



embryos develop the portions of the uterus containing these bunches 

 expand. This expansion continues until the enlarged spaces fill almost 

 the entire medullary portion, the tissue substance beween the different 

 regions of enlargement being reduced greatly in thickness but remain- 

 ing to the last to separate these chambers from each other (Fig. 43). 

 In no stage does the uterus force its way between the excretory ducts 

 and the ventral cortical layer. Thus here in the ripe uterus is a con- 

 dition that is very unusual in the Anoplocephalinae, and which indeed 

 has been observed in only one other species of the group, namely, 

 Schizotaenia americana. One recalls at once the uterus of the Lin- 

 stowinae, tho there is no indication that the uterus ever really breaks 

 down in the present species. It appears therefore it would not be cor- 

 rect to speak of the compartments as egg-capsules in the sense that the 

 term is used, even tho it is probably a step in that direction. 



Drawings by Stiles and Hassall (1893) of gravid uteri of Moniezia 

 pianissimo, and M. alba indicate structures which, tho not so repre- 

 sented, may be identical with the walls of the compartments found in 

 M. expansa. There is a slight indication of such structures also in their 

 drawing of the gravid uterus of M. neumanni. Their drawing of M. 

 trigonophora shows no such structures but since they give no indica- 

 tions of such structures in their drawing of M . expansa, the absence 

 means nothing. Thus no evidence available is opposed to the conclusion 

 that the Monieziae from mammals have the uterus similar in all essen- 

 tial respects to the condition here described for Moniezia expansa. The 

 excellent account of Fuhrmann (1902) shows however that the uteri 

 of the Monieziae from birds differ in almost every point from the type 

 just described. The difference between these two groups, if the condi- 

 tion for M. expansa is likewise the condition for other mamalian Monie- 

 ziae, may be summed up as follows : 



Monieziae from mammals Monieziae from birds 



Mature uterus crossing excretory Mature uterus not crossing excre- 



ducts tory ducts 



Mature uterus a complicated Mature uterus a simple transverse 



reticulum tube, or with a few simple 



branches 



Gravid uterus in the form of many Gravid uterus saccular, or with 



separated or nearly separted simple anterior and posterior 



compartments pockets 



Embryos with pyriform apparatus, Embryos without pyriform appara- 



the horns of which end in disk tus 



Dorsal excretory duct median to Dorsal excretory duct dorsal to 



ventral ventral 



