558 



XV, lig. 194) lo slugs (Limax), and laised the larval stage (PI. 



XVI, figs. 199-202) in twenty days. Slugs containing these lar- 

 vae were then fed to chickens, and within eight days the four 

 segments were formed. There can, therefore, be no question 

 that chickens become infected with this tapeworm by eating 

 slugs. 



Echinocotyle Rosseteri of ducks — Small fresh-water crusta- 

 ceans (Cypris cinerea)i containing a very characteristic larval 

 tapeworm (PI. XIX, fig. 251) were fed to a domesticated duck 

 by Rosseter (1891A-B, 1892). The duck was aftenvards killed 

 and found to be infested with tapeworms possessing the same 

 characteristic head (PI. XIX, figs. 247-248). The life history 

 of this form must therefore be looked upon as experimentally 

 demonstrated. 



2. Experimental infection of invertebrates by feed- 

 ing the eggs of avian tapeworms: 



Davainea proglottina of chickens. — This case has been dis- 

 cussed above. 



Drepanidotaenia anatina of ducks. — Schmidt (1894) has re- 

 cently demonstrated the life history of this worm in a manner 

 which places the source of infection beyond question. He fed 

 large quantities of tapeworm eggs to fresh-water crustaceans 

 (Cypris ovatai) and thus raised the larval form (PI. IX, fig. 

 110). In sum.mer these larvae developed in two weeks, but in 

 winter they required over five weeks for their development, the 

 difference in time being attributed to the difference in the 

 temperature. The same larval form is described by Mrazek 

 (1891) also from two other mussel crabs, i. e,, Cypris incon- 

 gruensi and Cypris compressai (=:2Cypria ophthalmica accord- 

 ing to Moniez). 



3. Comparison of tlie liooks upon the beads of the 

 adult tapeworms in birds with the hoolvs of larvae 

 found in invertebrates, and thus associating the young 

 and old stages. 



This method of explaining the life history does not 



iThere are no popular names for the numerous different 

 species of small fresh-water crustaceans. The popular name 

 mussel crabs is used for the Ostracoda (Cypris. Candona, 

 etc.); water fleas for Daphnia; copepoda for the Copepoda (Cy- 

 clops, ri. VT. fig. fi?: PI. XT. fig. ir!0): flea crabs for Gammarus. 



