401] AXOPLOCEPHALIDJE—DOUTHITT 51 



distinct; and except for Triplotaenia and Aporina they form a com- 

 pact and orderly group. But little attention has been given to the 

 relationships of these genera to each other. In the following pages the 

 various resemblances in the different organs are considered, with refer- 

 ence to the question of relationships between the various genera. 



1. The Structure of the Uterus. — Two general types of uterus have 

 been recognized in this group : the tubular, found in Bertiella, Anoplo- 

 cephala, and most Cittotaeniae,and the reticular, found in Andrya, 

 most Monieziae, and some Cittotaeniae. In addition the uteri of Schizo- 

 taenia, Triplotaenia, and Aporina have been recognized as each being 

 a distinct type in itself, tho the uterus of Triplotaenia is not really 

 different from the tubular. The uterus of Schizotaenia has been shown 

 in this paper to be of the reticular type, the reticulum being apparently 

 in the process of degeneration. There appears no reason to regard the 

 uterus of Aporina as of any other than the tubular type. As to the 

 relationships of the reticular and tubular types to each other, very 

 little has been done in the way of investigation except to conjecture. 

 Generally the reticular type has been supposed to be derived from the 

 tubular by the outgrowth and anastomosis of proximal and distal 

 branches. Following are offered the conclusions from studies of the 

 reticulate uteri of different species of Andrya, made with the view of 

 studying the relationships of these two types to each other. 



In the earliest stages in which indications of the uterus were 

 observed it occupies the entire region later occupied by the fully devel- 

 oped reticulum. This stage is long before any lumina appear. The 

 uterine tissue is more or less diffuse, there being no indication of segre- 

 gation along lines, except that it is more or less "stringy" in transverse 

 axis. As the proglottid increases in size, the cells segregate more and 

 more into definite lines which run in all directions and connect at fre- 

 quent intervals, forming a network. These lines of segregation do not 

 spread from any central locality but appear in situ and so far as could 

 be observed, at about the same time in all parts of the proglottid. Later 

 cavities appear in these tubes; these again do not spread out from any 

 central source but appear in situ and without the stimulus of entering 

 ova. When fully developed they form a continuous network of open 

 tubes. As these tubes become filled with ova they expand and 

 coalesce, forming a single saccular cavity. Development then proceeds 

 by regular outpocketing, anteriorly and posteriorly. Thus in the early 

 stages of development there is no indication that the reticulate uterus 

 has been derived from a transverse tubular type by outgrowth and 

 anastomosis of branches, as was suggested by Stiles (1896). It is true 

 of course that the uterus spreads from some original source in the course 



