270 ENTOZOA. 



sufficiently unfold the complexities of the process. Referring to 

 Naumjm's memoir (which I had myself previously consulted), 

 Leuckart (at s. 752 of his work ; bd. I.) makes the following com- 

 ment : — " Before I enter," he says, " on the formation, more espe- 

 cially of the secondary so-called daughter bladders, I will just 

 mention that Naumyn considers the echinococcus heads, as I have 

 also done, as taking their origin, without exception, on the brood- 

 capsules, and that in their normal condition they are always con- 

 nected in one common system with the maternal hydatid. In this 

 respect only is there any difference between us, namely, that Nau- 

 myn considers the hollow buds which adhere outside the brood- 

 capsules to be inverted and only formed during the cooling of the 

 echinococcus vesicle. In their normal condition the young echi- 

 nococcus heads were to protrude into the cavity of the brood- 

 capsule ; consequently, they there developed themselves (as Wago- 

 ner has also described) from the first, and in their subsequent state, 

 with the cuticular layer outside. That both conditions may appear 

 there can be no doubt, and I have particularly stated that I have 

 sometimes found the whole of the buds inverted. In spite of this 

 circumstance, I am inclined to consider my view, for the present, 

 the correct one, and in opposition to the view of Naumyn, to con- 

 sider the premature inverting as exceptional, partly on account of 

 the analogy with the other bladder tapeworms, partly, also, be- 

 cause after the representation of Naumyn (and Wagener) not a 

 single motive can be discovered for the development of echinococ- 

 cus heads from hollow buds. If the heads were to bud freely in 

 the cavity of the brood-capsules from the beginning, then one must 

 explain their later solid formation from the commencement. I have 

 never seen the cilia which, according to Naumyn, are situated on 

 the inner surface of the mother bladders, as well as on the brood- 

 capsules, but, in other respects, there are hardly any differences of 

 opinion between us as regards the histology of these animals. The 

 more striking, therefore, is the divergence of our views as to 

 the daughter hydatids. It is denied (by Naumyn) that they take 



