FURTHER INVESTIGATIONS BY THIS METHOD, AND THEIR RESULTS. 41 



to the Helminths. The development of these animals, which cer- 

 tainly closely resemble the Helminths in their parasitic mode of life, 

 was worked out by myself some years ago ; x I 

 succeeded in rearing the so-called Pentastomum 

 denticulatum in the intestine of the rabbit from 

 the eggs of Pentastomum tcenioides, and traced the 

 development of the young Pentastomum denticulatum 

 into the adult Pentastomum tcenioides by placing the 

 embryo in the nasal cavity of the dog. 



Although these results of experimental helmin- 

 thology appear so important and numerous, there yet 

 remains much to discover. There are always forms, 

 even among the most common of the Helminths, 

 whose origin is unknown. We must admit that 

 there is much in the natural history of parasites 

 that seems problematical and hardly explicable, in 

 accordance with our present experience, but who 

 would dare, in the face of all the results that have 

 been already achieved, to fill the gaps in our know- 

 ledge with the remnants of some antiquated theory ? 

 If Eudolphi and Bremser, and all the other cham- 

 pions of former helminthological theories, were 

 present to-day, they would lower their colours, and p I 

 refuse to renew the old disputes. The theory they 

 fought for is an error that has been dissipated. 



.27. 1 

 denticulatum. 



1 "Ban und Entwickelungsgeschichte der Pentastomen : " Leipzig, 1860. Preliminary 

 account in Zeitschr. f. rationelle Mcdicin, Bd. ii., p. 48, 1857 ; Bd. iv., p. 78, 1858. 



