557 



Tlic lifi' liistory of these wwms agrees with the life 

 history of other tapeworms; tlie ova of the parasites 

 are voided with the excremeut and are swallowed by 

 insect) and d(velo])s into 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 in(o a larval form, known in this 

 man as a cysticercoid. This larva develops into an 

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

 etc. 



The known or supposed life history has been based upon tour 

 different methods of work, 1. e.— 



1. Experimental infection of the fowls by feeding to them 

 known larval stages found in invertebrates, and thus raising 

 the adult stage. 



2. Exeprlmental infeetion 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 

 proof 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. 



The following are tlic data we have at present re 

 garding the life history: 



I. Kxperimenf.il iiifcrl ion of fowls wilh larv:ic 

 in invertebrates. 



Davainea prolottina' of [•hiekens.— Gassi & Rovelli (18!>?.. 

 1S89A, 1892) fed the eggs (PI. XV. ftg. 198) of this tapeworm (Pi. 



'There are as yet but few popular names for the various 

 poultry tapeworms. Several new popular names are 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 eases. 



