557 



The life liistoiy of those worms agrees with the life 

 histoiy of other tapeworius; the ova of the parasites 

 are voided with the excrement and are swaHowed bj' 

 insect) and develops iiilo a larval form known in this 

 an oncosphere) contained within the eggshell then 

 bores its way from the intestine into the body cavity 

 of the intermediate host (a worm, snail, crustacean, or 

 insect) and develops into a larval form, known in this 

 case as a cysticercoid. This larva develops into an 

 adult worm when swallowed by a chicken, duck, goose, 

 etc. 



The known or supposed life history has been based upon four 

 different methods of work, i. e.— 



1. Experimental infection of the fowls by feeding to them 

 known larval stages found in invertebrates, and thus raising 

 the adult stage. 



2. Exep'rimental infection of invertebrates by feeding to them 

 the eggs of tapeworms found in birds, and thus raising the 

 larval stage. 



3. Comparison of the hooks upon the heads of adult tape- 

 worms of birds with the hooks of larvae found in invertebrates 

 and thus associating the young and the old stages. 



4. Wild speculation as to the intermediate hosts, based upon 

 negative results and totally devoid of any scientific foundation. 



Of these four methods of work the first two give positive 

 pi'oof of the life history when the experiments are successful: 

 the third gives a probability to the statements, but not a 

 proof: the less said about the fourth method the bettter. 



Tlio following are the data we have at present re- 

 garding the life history: 



1. Experimental infection of fowls with larvae 

 in invertebrates. 



Davainca prolottinai of chickens.— Gassi & Rovelli (l.SS?., 

 18S9A, 1892) fed the eggs (PI. XV. fig. lOS) of this tapeworm (PI. 



JThere are as yet but few popular names for the various 

 poultry tapeworms. Se\ieral new poinilar names ai-e intro- 

 duced in the second part of this paper, but for the sake of 

 exactness and brevity it is necessary' to introduce the scientific 

 names in all cases. 



