272, DR. F. E. BEDDARD ON 
In both transverse and longitudinal sections only two large 
longitudinally running trunks of the water-vascular system are 
to be seen. These two trunks, as is so often the case, are of quite 
different dimensions. The dorsal tube, which is very much 
smaller than the ventral, lies above it, sometimes also rather to 
the inside, and has thicker walls. This tube is so fine that I have 
occasionally been unable to find it in a given section, though it 
would appear to be quite a continuous vessel. Below hes the 
very much larger ventral tube. Thisis situated at some distance 
to the inside of the nerve-cord. In the existence of but two 
principal longitudinal water-vascular tubes the present species 
agrees with the other two forms which are found in South 
American Marsupials, and also with the recently described species 
named by Zschokke Oochoristica rostellata *; in the latter case, 
however, the two tubes, dorsal and ventral, are of about the same 
calibre, as is shown in his figure of a transverse section through 
a proglottid of that worm. In longitudinal sections the same two 
tubes are always quite visible. 
To these two principal longitudinal tubes on each side of the 
proglottid a third may be added, which is, however, not comparable 
with the additional tubes found in certain species of Oochoristica 
from 8S. American Edentates. One does not find in transverse 
sections six conspicuous longitudinal vessels such as are so plain 
in an Oochoristica from T'amandua, upon which I have recently 
reported to the Society. But, on the other hand, the anastomosis 
between the branches of the excretory network which pervades 
the segments does lead to the formation of at least short longi- 
tudinal trunks. I have observed such a one lying outside of the 
nerve-cord. The branches of the water-vascular system in this 
species are indeed very copiously developed. Four or five, or 
even more, large branches from the ventral vessels pass across 
the proglottids, and even more are directed towards the lateral 
margin passing across the nerve-cord. The whole body is, in fact, 
richly supplied by a plexus, of which the individual tubes are 
often wide. I have not been able to ascertain whether any of 
these branches perforate the cortex and reach the exterior of the 
body. 
§ Male Gonads and Ducts. 
The relative positions of the male and female gonads in this 
group are frequently made use of as a generic distinction. The 
present genus, Oochoristica, has been partly defined thus by 
Ransom + :—“ Testicles numerous, surround female glands pos- 
teriorly and on the sides.” The figure given of O. rostellata by 
Zschokke t is in accord with this definition; and so are certain 
of the figures given by v. Janicki§. Not, however, his illus- 
trations of the species O. bivittata and O. didelphydis, which are 
* Zeitscbr. wiss. Zool. Bd. Ixxxiii. 1905, pl. i. fig. 2. 
+ Bull. U.S. Nat. Mus. No. 69, 1909, p. 85. 
Zeitschr. wiss. Zool. Bd. Ixxxiii. 1905, pl. 1. fig. 3. 
a 
§ Tbhid. Ba. lxxxi. 1906, pl. xx. figs. 5, 7, pl. xxi. figs. 18, 21. 
