360 



THE DEVELOPMENT OF CE3T0DES. 



The worms then remain for a while free in the body-cavity, but after 

 some weeks one finds them once more in a cyst hanging usually to 

 the omentum or the connective-tissue covering of the intestines. The 



Cysticermis tenuicoUis of our rumi- 

 nants behaves in an exactly 

 similar way, as we shall after- 

 wards notice in greater detail. 



According to the observa- 

 tions on which we rely, the de- 

 velopment of the cystic worms 

 always begins with the formation 

 of the subsequent bladder. As 

 FiQ. 207.— A piece of rabbit's liver with to the Origin of the latter, we 



pa,Baa,geB oi Cysticerous pisiformis. ( x 10.) have nO direct results, but We 



can hardly be mistaken in regarding it as the enlarged and 

 modified embryonic body.^ This supposition becomes a certainty 

 when we examine the more microscopic so-called " Cystieercoids," 

 which resemble the above-described bladder-worms in all essentials, 

 differ only in their minuteness and in the absence of fluid. 



These parasites are found ex- 

 clusively in cold-blooded animals, 

 especially among invertebrates, 

 such as insects and molluscs. As 

 yet but few forms are known — not 

 more than a dozen — although we 

 have reason to believe that they 

 far exceed the bladder -worms 

 proper in the number of their 

 species. 



In one of these forms, to 

 which we have already (p. 331) 

 referred — the Cysticercus tene- 



„ , . ^ . hrionis, which is probably the 



Fio. 208. — Development of Cyshcerons p m ■ • i i -j.- 



tenebrionis (after Stein). A, Embryo after yOUng stage of a Tcema mhabltmg 



the hooks are cast off ; 5, Adult (72/s«icerc«s. t^g mouse — Stein has described 



(x about 100.) . J , „ ,, 



the gradual passage or the em- 

 bryonic body into the subsequent bladder. The six-hooked embryo 



■ I believe that I once found the six embryonic hooklets near the anterior end of the 

 body of a young Cysticercus pisiformis (" Blaseubandwiirmer," p. 120). Professor Ed. van 

 Beneden has, he tells me, been more fortunate, having repeatedly demonstrated these hooks 

 on bladder-worms of Taenia saginata 0'4 to 0'5 mm. in size. Three times all the six hooks 

 were present in varying position, while in other cases we could see only a few, or only one. 

 [Baum also (loc. cit. supra) appears to have several times found the embryonic hooks in 

 young specimens of Cysticercu8 pisiformis, whose heads were still undeveloped. — E. L.] 



ercus pisiformts, whose heads we 



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