82 PEOF. T. S. COBBOLD ON A 



M. Duchamp quotes freely, and with uniform accuracy, from Die- 

 sing's writings (botli from tlie ' Systema ' and bis various ' Eeri- 

 sionen'), and yet it is Diesing who refers to Ligula reptans as occur- 

 ring in Reptiles, Amphibia, Aves, and Mammalia. In connexion 

 with the data supplied by Manson's " find," it is interesting to 

 observe tliat in all the birds and quadrupeds proper, and also in 

 the bats and marmosets in which a ligule has been found, the 

 parasite was always either situated within tlie muscles or in 

 subcutaneous follicles. This, at least, shows a similarity of 

 habit ; and if Ligula reptans were possessed of a longitudinal 

 groove and were not furnished with cephalic pits, one might 

 suppose it to be identical with L. Mansoni. Again, the external 

 characters rather forbid our connecting tlie liuman ligule with 

 Ligula nodosa of the trout, though such identity, if proven? 

 might help to explain the origin of L. Mansoni. 



As already pointed out in my larger treatise, the observations 

 of M. Duchamp, taken in connexion with the embryological 

 studies of the late Dr. Bertolus, render it extremely probable 

 that the trout's ligule is the sexually immature state of the 

 great broad tapeworm of man. If this genetic relation should 

 be established by further researches (as in all probability it will 

 be), it is possible that the proscoleces or six-hooked embryos of 

 Bothriocephalus latus might, in place of passing through the 

 ordinary intermediate piscine host, develop as immature ligules 

 within the human body. We know that phenomena precisely 

 analogous to this do actually obtain in the case of Taenia solium, 

 tlie proscoleces developing into scoleces or Cysticerci within the 

 human territory instead of passing into the flesh of swine. In 

 this case the ultimate host becomes also (for the subsequent 

 generation) the intermediary bearer ; an act of cannibalism would 

 certainly bring about the completion of the genetic cycle. 



In this explanation I cannot take into account the possibility 

 of any Cestode dimorphism such as M. Megnin argues for so 

 warmly in other cases. I do not believe that it has been proved 

 in any instance of tapeworm life. Here, I think, we are only 

 entitled to conclude that the Chinese host becaaie victimized by 

 his having swallowed the six-hooked embryos of an adult Cestode 

 of some kind or other. In all likelihood the worm was either a 

 Ligula or a Bothriocephalus. In any case the phenomenon was 

 probably an instance of " straying." If so, we ought to be able to 

 identify Ligula Mansoni either with some hitherto known sexually 

 immature ligule or with a form yet to be discovered. 



