ABSENCE OF AN EXCEETOEY SYSTEM. 601 



those above mentioned ; and also distinct calcareous corpuscles of 

 varying, and sometimes very considerable size. They are usually of 

 a lenticular form, and agree in appearance (lamination and apparent 

 formation of nuclei) with the corresponding structures of the related 

 worms, although they diifer from them in becoming pale on the appli- 

 cation of acids, without evolution of gas. They are usually found 

 singly, and are distributed over the whole surface of the worm. 



Since we noticed in the other bladder-worms that the appearance 

 of the first calcareous corpuscles was associated with the development 

 of the excretory vascular system, it might be supposed that the 

 Echinococcus also would be furnished with a similar apparatus. This 

 supposition seemed all the more probable from the fact that, according 

 to Naunyn's observation, the worms, even when of the size of a pea, 

 exhibited a lively ciliary motion. The cilia were sometimes placed 

 singly at some distance from each other, and at other times in groups 

 of five to ten. They were not, however, situated on the parenchyma- 

 layer itself, but, strange to say, on its inner surface, so that they pro- 

 jected freely into the interior of the bladder. At first they were only 

 small, so that it was difficult to determine their form ; but afterwards it 

 was seen that at the lower end, by which they were attached to the 

 cellular layer, they were spherically thickened, and thus probably 

 always belonged to only one cell. 



But in spite of this, neither Naunyn nor I have succeeded in 

 proving the presence of a vascular system in this parasite. It is true 

 that the cellular layer has, deep down, a peculiar system of net-like 

 anastomosing cords of more or less considerable thickness (as much as 

 O'OOS mm.), but these cords do not give one the impression of vessels. 

 They appear rather to be solid bands of a homogeneous substance, 

 and are, as Naunyn says, similar to those which are seen by the 

 microscope on a glass smeared with fat or oil. 



The ease with which they are destroyed renders the investigation 

 of these structures specially difficult. One needs only to expose the 

 worm for a short time to the influence of water or cold, or to press 

 the preparation roughly, to witness the immediate shrivelling up of 

 the former cords. Instead of the network, one finds in such cases 

 large round drops of a sarcodic nature. Similar results are produced 

 by the use of chromic acid and of Weissmann's solution of caustic 

 potash (36 per cent.). 



Since the network is not a vascular apparatus, it might perhaps 

 be supposed to be contractile in function. But this interpretation is 

 also inadmissible ; not, however, because muscular fibres are altogether 

 absent from the Echinococcus, as was before erroneously supposed, but 

 because these muscular.fibres„ which one caa, hardly fail to see in the 



