86 T. B. ROSSETER ON THE GENITAL ORGANS OF TAENIA SINUOSA. 



the branchiae (see Rosseter on " Trichodiria as an Endoparasite,"' 

 Journ, R. M.S., Ser. 2, Vol. VI., 1886, p. 929). The fact of these 

 platyhelminths being endowed with organs of generation which, 

 although hermaphroditic, are comparable favourably with the 

 bisexuality of the higher orders of nature, and are yet anenterons, 

 does not necessarily imply that they previously were enter itic r 

 but having by disusage, caused possibly by their surrounding- 

 environments, lost the organs of nutrition, from this cause 

 had thus retrograded in the scale of life. Far from it : I main- 

 tain that these platyhelminths never possessed an enteron. No 

 matter what stage of segmentation in the strobila you examine, no 

 trace of such a tract can be found existing, or as having existed, 

 in their cellular tissue. I have looked in vain in prepared and 

 stained sections, and have never been able to resolve Pagen- 

 stecher's narrow space within the muscular layers {Taenia critica) 

 which he would represent as the body cavity ; neither can the 

 " anlage " of the digestive apparatus (?) be traced in the embryo 

 or hexacanth stage. Nor is the saccular cavity of the cyst 

 (Cysticercus) to be looked upon as an enterocoele ; it is merely 

 the blastomeric cavity of the forming strobila. Thus we are 

 forced to consider this cavity as a blastocoele ; consequently, it 

 has never arrived at, much less passed through, in the law 

 of development, the gastrula stage. Looking at it from this 

 point of view I arrive at the conclusion that a close affinity 

 exists between the Cestoidae {Taenia si?iuosa) and the Porifera- 

 Spongidae. One can trace this affinity backwards through 

 Twrbellaria convoluta, which, like the Cestoidae, ingests its sus- 

 tenance through the endodermal parenchyma ; likewise in the 

 Discophora, in which is foreshadowed by the agamogenetic multi- 

 plication of the colonies by fission, into eight-lobed discoidal 

 medusoids {Medusa bifida), the future strobila of the Taenidae ; 

 and finally in the lowest groups of the Metazoa, the Porifera,. 

 the cellular tissue of the one is structurally the counterpart 

 of the other. That which I wish chiefly to draw attention 

 to, however, is the spiculiferous character of the Porifera and 

 its relationship, or affinity, in this respect, with the Cestoidae,. 

 more particularly as regards Taenia sinuosa. 



