74 ANIMAL PARASITES. 



vesicle. Up to this time only Accphalocysts which belong to 

 Echinococci, and one which probably belonged to Cysticercus 

 tenuicolUs, have occurred. They become destroyed at last in the 

 body of their host, in the same way as the corresponding pro- 

 liferant forms. 



If the six-hooked cestoid-brood gets into animals which are 

 not suitable to it, or into such organs in an animal otherwise 

 suitable, as are not adapted for the particular species of cestoid 

 worm, it is destroyed in a very short time, usually even in the 

 few first days after its immigration. The form which they 

 acquire we have already referred to, and indicated that a con- 

 fusion of them with miliary tuberculose disease of the organ, 

 is not onty possible, but may frequently have occurred. If any 

 one wishes to obtain a knowledge of trulv straved cestoid 

 embryos, he has only to administer mature proglottides to 

 various animals, and he will then find that he meets with 

 a greater number of strayed individuals in an animal the sooner 

 it is dissected after an administration, and also the narrower 

 the limits of the normal diffusion and thriving of a species 

 in the body of an animal. Thus, in Ccenurus, which is so 

 extraordinarily limited in its dwelling-place (the brain, and 

 perhaps the spinal marrow), we find the most frequent wan- 

 derings, but far more rarely in Cysticercus celluloses, destined to 

 dwell in the cellular tissue, which is distributed through the whole 

 body, and in Echinococcus which is also widely diffused in the 

 body. But it is quite unjustifiable to call those cystic worms 

 strayed which have arrived at full development, like other crea- 

 tures of their kind, but which occur in places with regard to 

 which we cannot easily understand how the cystic worm could 

 get from them into the intestine of the animal in which it 

 becomes converted into a Tcenia, of which we shall speak here- 

 after. I will not indicate, with Leuckart, that in this case the 

 brood of a frog which has got into a puddle which has dried 

 up before its evolution, is also to be called strayed, and will not 

 devote any space to the above question. But I cannot sup- 

 press here, that I am firmly convinced that we do not jet 

 know any species of Cestodea which becomes developed to the 

 second stage in one species of animal, unless this animal — except 

 where civilisation may have introduced here an artificial, insur- 

 mountable hindrance — can be devoured by the animals in whose 

 intestine these vesicular worms are capable of becoming mature 



