TWO NEW TAPEWORMS. 



699 



observed, and to some extent a retiform condition obtains, 

 though not so clear as in some other tapeworms. The cavities 

 contain many ova. The walls of the cavities are distinct and 

 nucleated. The suggestion is of flattened cells, and the edges of 

 the cavities which are the actual walls are differentiated from the 

 surrounding parenchyma by a firmness which is marked by a 

 deeper staining. In the greater development of what is obviously 

 a uterus, the present species is plainly nearer to 0. marmosce 

 than to L. ameivce. It differs from both in the fact that the 

 ripe embryos, when scattered through the parenchyma after 

 the disappeai^ance of the uterus itself, are not so closely packed. 

 In sections the ripe proglottids seem to contain fewer embryos. 

 Moreover, the individual embryos lie more loosely in the spaces 

 which they occupy. These spaces show no nucleated walls of 

 their own. The embryos extend into the cortex. I could only 

 detect two membranes surrounding the embryo. The embryos 

 appear to be larger than those of 0. marmosce. 



Systematic Position of Linstowia lemuris. 



The species which has just been described must be, as I think, 

 referred to one of the two genera Linstotvia and Oochoristica. The 

 combination of characters shown in the possession of a totally un- 

 armed scolex, single generative organs, a uterus of more or less 

 detached cavities, the final imbedding of the embryos singly in 

 the parenchyma, is unknown elsewhere than in these two genera. 

 I have already, in describing Linstotvia ameivce and Oochoristica 

 inarmosce, pointed out the impossibility, or at least great diffi- 

 culty, in rationally distinguishing between these two genera 

 and need not recapitulate here the reasons there given. I may, 

 however, point out what I did not there mention, except by 

 implication, that the founders of the two genera defined them at 

 very nearly the same time (either at the end of 1898 or at the 

 beginning of 1899). Furthermore, neither Zschokke (who is 

 responsible for Linstowia *) nor Liihe t (who defined Oochoristica) 

 mentions the work of the other. It is doubtful, therefore, 

 Avhether both genera would be accepted now by these two 

 authors, were they founding them afresh with knowledge of 

 each other's work. I am, however, obliged to admit that 

 Zschokke in a more recent + communication accepts Oochoristica 

 without comment, and contrasts its distribution with that of 

 Linstotvia. I myself believe, on further consideration, that 

 Oochoristica will be found to difier by the condition of the 

 uterus — a suggestion which I have already made, but which 

 requires confirmation by an examination of the other species 



* The genus was actually defined 13}' Zschokte in Zeitsclir. f. wiss. Zool. Bd. Ixv. 

 p. 441, not in his account of two species in Semon's ' Foischungsreise,' which is 

 sometimes quoted as the reference for the genus. 



t Zool. An/,. Bd. x\i. p. 650. 



X Zool. An/.. Bd. xxvii. p. 290. 



48* 



