TWO NEW SPECIES OF CESTODES. 281 
filling all the available space in the proglottid; cirrus-sac small, 
opening into a genital cloaca in front of vagina; sperm-duct with 
a loose coil dividing up into a meshwork of ductules. Ovary anterior 
in position ; vagina with cylindrical receptaculum ovorum. Uterus 
consists of a posteriorly situated and transverse tube, from which 
arise numerous diverticula, extending ultimately through most of 
proglottid ; uterus finally disappears, leaving embryos scattered 
singly throughout parenchyma, extending here and -there into 
cortec. Hmbryos with two shells. 
Hab. American Marsupial, Marmosa elegans. 
S$ The Genera Oochoristica and Linstowia. 
The fact that Linstowia and Oochoristica are placed in separate 
families by systematists at present has tended of itself to 
exaggerate the differences which exist between these genera. 
Their real propinquity, however, becomes very apparent when 
we wise the “ Key to Genera” devised by Mr. B. H. Ransom *. 
In this dichotomous table we pursue the two genera side by side 
until the very last of the characters made use of ; they are in 
this differentiated by the thickness of the cortical layer and the 
position of the testes in the proglottid. It should be noted that 
this dichotomous table and the subsequent generic definitions f 
given by Ransom were published after the information gathered 
by Zschokke and v. Janicki had been put forward. 
When we come to look into the characters of the known 
species, including those deseribed in the present communication, 
that have been referred respectively to one or other of the 
genera Linstowia and Oochoristica, it does not appear to be at all 
an easy matter to draw many hard and fast lines of separation. 
The first-described species of Linstowia, not then referred beyond 
Tenia by its original describer {, has been investigated in further 
detail by Zschokke§. The salient characters of this worm are 
the following :—The cortex is thick ||; the longitudinal muscle- 
bundles are in two rows, of which the inner is the thicker, but 
the bundles have not more than four or five fibres each; the 
genital cloaca is deep; the cirrus-sac is very large; the vas 
deferens is coiled and dilates posteriorly, just before it begins 
to divide, into a kind of vesicula seminalis; the testes extend 
through the proglottid dorsally ; the vitelline gland is quite. 
posterior in position and nothing lies behind it. The excretory 
tubes he side by side, and are formed by a transverse vessel in 
each segment as well as by a network. 
Zschokke gives in the same work a fuller account of a second 
species, viz. Linstowia semoni, an example of which serves to 
fill up certain lacune in the generic characters. Of this worm 
* Bull. U.S. Nat. Mus. No. 69. 1909, p. 53, &c. + Loc. cit. pp. 65 & 84. 
+ D’Arcy Thompson, Journ. Roy. Micr. Soc. 1903. 
§ Zschokke in Semon’s Forschungsreise, etc., 1898, pl. xiv. figs. 1 & 2. 
|| Thompson, Zoe. cit. pl. v. fig.8. A transverse section is not figured by Zschokke. 
