34 



JOHN E. GUTBERLET 



scolex of the adult is between four and five times as large as that 

 of the cysticercoid. The scolex of the cysticercoid has as yet 

 not functioned so that the musculature of the organs is not devel- 

 oped as in the adult, consequently is not nearly as massive. The 

 cells also are smaller than those of the adult. 



Schmidt (1894: 10, 44) shows that the adult scolex of Dre- 

 panidotcBnia anatina is about three times as large as that of the 

 cysticercoid. He also states that the size of the cysticercoid may 

 vary with the size of its host. 



Different forms become modified in changing from the inter- 

 mediate to the adult hosts as shown by Schmidt (1894) in Dre- 

 panidotcrnia anatina, Rosseter (1891) in Echinocotylus Rosseteri, 

 and Grassi and Rovelli (1892) in Davainea proglottina. 



Onchospheric hooks in the wall of the tail are the same size 

 (18/a) and shape as those of the embryos found in the mature 

 proglottids. 



A consideration of these factors of morphological significance 

 which demonstrate the resemblances between the cysticercoid and 

 adult, indicates clearly that this cysticercoid is the intermediate 

 stage of Clioanotcrnia infundibuliformis. 



OTHER CHICKEN CESTODES IN THE UNITED STATES 



1. Davainea tetragona (Molin 1858) Blanchard 1891 

 Diagnosis: Length 10 to 250 mm. by 1 to 2.5 mm. in breadth, 

 varying with state of contraction. Scolex (Fig. 19) 175 to 215;Lt 

 in diameter, with retractile rostellum 25 to 50/z in diameter, armed 

 with single row of about 100 hooks. Rostellar hooks (Fig. 20) 

 6 to 9/i long through longest axis, hammer-shaped, with long ven- 

 tral root and short dorsal root, prong short and recurved. Suckers 

 oval, 60 to 110/1 in diameter, armed with 8 to 10 rows of small 

 hooks of various sizes. Acetabular hooks (Fig. 21) range in 

 size from 4 to 8fi through longest axis, having thorn-like 

 prong, short dorsal root, and longer flattened ventral root, which 

 is shorter than prong. Neck long and slender, but often as broad 

 as head. Segments trapezoidal and imbricate, edges of strobila 

 serrate. Oldest segments usually longer than broad, often bell- 



