706 ON TWO NEW TAPEWORMS. 



ill various definitions, it is so fai' not clear what the asserted 

 implantation singl}^ of the ripe embryos means. The examination 

 of mature segments allows me to clear up this matter as to the 

 main facts of classificatory importance, at any rate. In com- 

 paring these conditions with those already referred to in Linstoioia 

 there is at first sight some difference in general appearance, which 

 is really due to the laxity of the ground-tissue of Linstowia, as 

 compared with the denser medullary tissue of Cotugnia. But 

 there is no morphological difference that I can detect. In both 

 the embryos are scattered not very closely (text-fig. 3) through 

 the medullary parenchyma and extend into the cortex. Each 



Text-figure 4. 

 B. 



A more highly magnified representation of the embryos of Cotugnia margareta. 



A. the thick outer shell. B. the indistinct middle shell. C. the inner shell 

 immediately surrounding the embryo. 



embryo fits its cavity completely, and I have never seen more 

 than one lying in one space of the parenchyma. This cavity, 

 moreover, has no. definite walls of its own. The uterus in 

 younger stages consists of scattered spaces, in each of which may 

 lie several ova, though sometimes only one. The uterus of this 

 Davaineid seems, therefore, to be similar to that of Linstowia. 

 The fully ripe embryos are surrounded by three egg-shells (text- 

 fig. 4). The outermost is very thick and often locall}^ thickened 

 to form boss-like prominences which may be even narrow and 

 prolonged. The embryo itself is immediately encircled by a thin 

 shell, and between the two a third shell is often to be detected. 



