H. A. Baylis 
413 
Oochoristica ( marmosae ). 
Ova from the first confined to the uterine 
cavities. 
Uterus persists through a good many segments. 
Oochoristica sp. from Tamandua. 
Egg-containing spaces in parenchyme have a 
definite cellular wall. (Figured by Beddard, 
1913, p. 875, text-fig. 149.) 
Linstowia (ameivae). 
From the first some of the ova are found in the 
parenchyme between the uterine cavities. 
Uterine cavities exist for a much shorter 
period. “The uterus seems to be degenera¬ 
ting... as compared with that of O. trvxr- 
mosae.'" 
Egg-containing spaces have no definite 
cellular wall at any stage. 
These characters, it must be admitted, are by no means definite—indeed, 
Dr Beddard evidently puts them forward chiefly as affording a possible means 
of separating off the South American forms parasitic in mammals from other 
species of the two genera. As he states, “ it is. . . next to impossible to separate 
the genera if we accept the present distribution of species among them/’ 
As regards the characters afforded by the uterus and the egg-capsules, the 
two species here described do not seem to afford much help in defining the 
limits of the genus. On the whole, they agree better with the account of 
0. marmosae than with that of L. ameivae , but there are certain points in which 
they diverge from it. Thus there is a definite, though very thin, cellular lining 
to the walls both of the uterus and of the parenchyme-spaces; yet the latter 
are not thick-walled embryo-sacs such as Beddard has described and figured 
for the species from Tamandua , which is ascribed to Oochoristica. Again, the 
arrangement of the egg-membranes, as already noted, is like that of Linstowia 
ameivae and of Oochoristica rostellata Zschokke, and unlike that of 0. marmosae. 
Other characters such as the relative thicknesses of the cortical and 
medullary parenchyme, and whether the testes do or do not extend across the 
whole of the dorsal side of the segment from back to front, are, as Beddard 
concludes, probably of little value in distinguishing between the genera. There 
are, however, two points mentioned in Ransom’s (1909) diagnoses, which 
might on further investigation prove to be important. These concern the 
arrangement of the genital pores, and the course taken by the genital canals. 
The former are said to be irregularly alternating in Oochoristica , and regularly 
so in Linstowia. The vas deferens and vagina, in Linstowia , are said to pass 
ventrally to both pairs of excretory vessels and to the longitudinal nerves, 
while in most of the species 1 ascribed to Oochoristica in which the point has 
been studied (though this is not mentioned by Ransom), they follow the more 
usual course between the dorsal and ventral vessels and dorsal to the nerves. 
This at least is the case in 0. rostellata , 0. truncata , 0. zonuri , 0. agamae and 
Beddard’s species from Tamandua 2 . 
If a distinction is to be made at all, it seems not unlikely that the name 
1 In certain forms from Marsupials and Edentates the genital ducts are said to pass dorsalh / 
to the excretory vessels. 
2 Beddard (1914) does not mention this point in the case of Linstowia ameivae and Oochoristica 
marmosae. 
