102 ANIMAL PAKASITES. 



tunately, we are completely in the region of conjectural zoology ; 

 but I am firmly convinced that my colleagues, who live in the 

 districts infested by Bothriocephalus, and especially on the sea- 

 coasts, will not be long before they give us the explanation. 

 The first thing to be done is to administer the mature ova of 

 Schistocephalus dimorphus (Creplin), from the intestinal canal 

 of certain marine predaceous birds, to sticklebacks, or other 

 small sea-fishes kept in a confined space, in order to see 

 whether or not numerous immature Schistocephali are developed 

 in the intestine of the fish itsetf. If not, we are certainly 

 justified in supposing that the stickleback first derives the 

 scolex from one of the animals on which it feeds. If Sc/iis- 

 tocephali are produced, we must suppose that the active migra- 

 tion of the young does not take place in these animals, but that 

 there is only a passive transportation from one intestine to 

 another, and that this is sufficient for development. In such 

 cases the young must certainly be bookless, and similar in form 

 to the mature animals, in which latter case it would also be 

 conceivable that species of cestode worms may pass through their 

 entire development in the same alimentary canal. 



If we apply what we have just discussed at length to the 

 Bothriocephalus latus of man, we must admit that we have no 

 data as to the production of this worm in the human subject ; 

 we do not know what migration the youngest brood makes, or 

 when it becomes converted into a scolex. In the obscurity pre- 

 vailing here, all attempts to furnish hints will certainly be 



fishes. These forms were employed by me to demonstrate the untenability of Dujardin's 

 and Von Siebold's opinion, that the Cysticerci were formed subsequently from developed 

 cestoid heads. But I also administered these Cestoidea obtained from the intestine of 

 the rabbit to dogs, in order to see whether Tannia scrrata may be raised from them, or, 

 in fact, to ascertain whether, after this second transference, these creatures continued 

 their transformation in exactly the same way as the true Cysticerci of the rabbit. I fed 

 a dog with five of these young Teenies, which I had bred in the intestine of a rabbit from 

 Cysticerci of the same animal. In eight days the dog exhibited no Tcenia serratce. 

 Whether subsequent experiments will furnish results, I must leave for further informa- 

 tion. It will be seen from this, that I endeavoured in this way, per analogiam, at once 

 to solve the question whether those band-like scolices of the fishes had probably been 

 first in another animal, and might have been produced from scolices which had already 

 been exposed to a migration into an unsuitable intestine. I say expressly, only " might 

 have been produced," and not "must have been produced " as I only offered a substitute 

 for an experiment, but must leave the direct proof to experimenters living on the sea- 

 coast. 



