POSSIBLE ABSENCE OF THE CYSTICERCOID STAGE. 365 



appearance and character simply as a process from the head-bearing 

 anterior end, belonging to it much in the same way as the neck 

 portion of an Echinococcus to its head. Here we find in an exaggerated 

 degree the same structure as we formerly noted in regard to the 

 " parenchymatous Cysticerci." 



It seems doubtful whether we can refuse to recognise at least the 

 genetic identity of the sac-like external body of this Cysticercus with 

 a caudal bladder, especially since the results of the discoverer's x inves- 

 tigations, which were controlled and corroborated by myself, make it 

 probable that the subsequent external body is formed directly from 

 the six-hooked embryo. The details of the development are unfor- 

 tunately unknown; we only know that the immigrant embryos, 

 before the loss of their hooks, grow to about half the size of the 

 Cysticercoid, and change their original shape for a somewhat 

 pear-like form. The embryonic hooks are not to be found on the 

 adult Cysticercoid. 



We must, moreover, admit the possibility of the young tape-worm 

 being developed by a simpler process than through the Cysticercoid 

 form. I am led to this admission partly by a communication of Dr. 

 Gruber's in regard to a young Tcenia, which he has since described 

 elsewhere, and which he found in investigating the littoral fauna of 

 the Boden See. 2 It was a worm about a millimetre long, which was 

 found stretched out in the body-cavity of Cyclops serrulatus, occupying 

 almost the whole space above the alimentary canal between eye and 

 abdomen. Special parts could hardly be distinguished; the body 

 consisted of a clear mass, with uniformly diffused calcareous bodies ; it 

 had a simple cylindrical form, and was furnished at the somewhat 



FIG. 212. Young form of Tasnia torulosa (?) in Cyclops serrulatus. after 

 Gruber. ( x 25.) 



thickened, hookless, anterior end with four distinct suckers. In the 

 great multitude of infected Cyclops, it was difficult to find the previous 

 stages. None of these, however, had the form of a Cysticercus. They 



1 Melnikoff, " Ueber die Jugendzustande der Taenia cucumerina," Archivf. Naturgeach., 

 Jahrg. xxxv., Bd. i., p. 69, 1869. 



3 Zool. Anzeiger, Jahrg. i., p. 74, 1878. 



