282 DR. F. E. BEDDARD ON 
there is no transverse section figured to show the relative thick- 
ness of the cortex. The water-vascular system, not figured in 
L. echidne, has as main trunks two tubes on each side, which 
later lie parallel, and not one above the other, which is the case 
anteriorly ; of these the dorsal tube lies to the outer side of the 
ventral. There is also a transverse trunk to be seen in each 
segment. The vagina in this as well as in the last species 
possesses a dilatation usually termed the receptaculum seminis. 
The uterus “ forms a thin-walled folded tube where the wall is 
early lost” *, and the eggs come to be imbedded singly in the 
parenchyma. ‘To these descriptions of the two species it should 
be added that in both the scolex is unarmed, that the genital pores 
alternate, and that there is nothing remarkable in the structure 
of other organs which have not been mentioned. 
If we contrast with these species certain forms which have 
been referred to the genus Oochoristica from Kdentates rather 
marked differences at once appear. In such formsas O. wageneri 
and the allied form which I have myself + lately described also 
from the Lesser Anteater, which may or may not be identical with 
it, we find the following assemblage of characters. While they 
agree with the members of the genus Linstowia, already referred 
to, in the unarmed scolex, the alternate generative pores, and the 
imbedding of the ripe eggs singly in the parenchyma, they differ 
by the much more complex water-vascular system consisting of 
six longitudinal tubes; they have also a small cirrus-sac which 
does not extend far into the body, not reaching much if anything 
beyond the nerve-cord. If these two groups of species comprised 
all that were known, the separation of the two genera would be 
quite easy and obvious. But there are forms which render such 
a demarcation impossible. 
In O. rostellata of Zschokke £ there are but two water-vascular 
vessels ; though these vessels are superposed instead of lying side 
by side as in Linstowia. On the other hand, in Linstowia theringi 
and Z. brasiliensis the cirrus-sac is as small as in Oochoristica ! 
While in the species described in the present paper as Linstowia 
ameive, the cirrus-sac is large (as in the Australian members of 
the genus Linstowia), and the testes are as markedly behind 
the ovaries as in Janicki’s species Oochoristica bivittata. As for 
differences in the relative thickness of the cortex and medulla 
insisted upon by many, I can see no difference worth mentioning 
in the figures of Oochoristica wagenert and Linstowia brasiliensis 
given by v. Janicki§. 
It is thus next to impossible to separate the genera if we 
accept the present distribution of species among them. Nor is 
the matter ameliorated if we make the planes of division some- 
what different. It had occurred to me to separate off the 
* For the species of Australian Linstowia, see also Zschokke in Zeitschr. f. wiss. 
Zool. Bd. lxv. (1899). 
+ P.Z.S. 1912, p. 627. t Zeitschr. wiss. Zool. Bd. Ixv. 
§ Zeitschr. wiss. Zool. Bd. lxxxi, text-fig. 4, p. 534, & pl. xx. fig. 2 
