T^NIA ECHINOCOCCUS. 257 



it, and have disappeared. Shortly afterwards the ovarium hkewise 

 vanishes, and then the development of the embryo commences in 

 the interior of the uterus. The opaque body which is present in 

 the other tapeworms, forming a central point of the entire female 

 apparatus, and which, in all probability, serves as the place of egg- 

 formation, is here altogether wanting." If this description be 

 correct, we have here a singular reversal of the relative position of 

 the parts as ordinarily seen in cestodes, and a remarkably early dis- 

 appearance of the organs primarily concerned in the development 

 of the eggs. 



Development. — On this head a great deal has been written, but 

 the limits of this work will forbid my giving more than a gene- 

 ral outhne of the subject, avoiding, in some measure, the controver- 

 sial points. In the main, no doubt, the developmental features of 

 this species can be made to harmonize with those already set forth 

 as regards the other cestodes, but the variations of detail and com- 

 plexities arising out of unusually pecuhar appearances render it no 

 easy task to trace out all the phenomena as they successively come 

 to light. Without further comment, I proceed to remark that the 

 eggs, supposed to be about five thousand in number in a full 

 grown joint, develop in their interior the usual six-hooked em- 

 bryo. These embryos are introduced into our bodies (and into 

 those of other parasite-bearers) by our partaking of water, or food 

 into which the eggs have been carried by accident or otherwise. 

 After arriving within the apparently selected host, the behaviour 

 of the embryos accords, at least, in the first instance, with that of 

 other tapeworm proscolices. With an especial liking for the liver, 

 they bore their way into this organ, or are carried along the circu- 

 lating current into other organs. In these situations they sooner 

 or later become transformed into simple vesicular, bladder-hke 

 bodies, commonly called acephalocysts or hydatids. 



Thus far, it will be seen, the larval development strictly con- 

 forms to that ordinarily observed in cestoda, but from this period a 

 series of changes occur which are not only unique in themselves, 



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