502 HARRY M. MILLER, JR., AND FLORA E. NORTHUP. 



extension of living cercaria 630/11); tail about 330 M in length. 

 Oral sucker 42 n, ventral sucker 64 n in diameter. Mouth sub- 

 terminal, short prepharynx, pharynx, wide esophagus bifurcating 

 into ceca extending to extreme posterior part of body. Granular 

 cytoplasm of small glands around esophagus and portions of 

 contents of esophagus and ceca stained deeply with neutral red ; 

 dorsal gland cells eosinophilic and ventral ones chromophobic in 

 sections; fine bundles of minute ducts passing through oral 

 sucker and opening on anterior end. Many rod-filled cysto- 

 genous glands l in dorsal part of body; stained deeply with iron 

 hematoxylin in sections. Excretory vesicle averaging 36 p. in 

 diameter; arms filled with refractile concretions, of double 

 coffee bean shape. Excretory system pattern not completely 

 worked out; of type of C. complexa Faust (1919); twelve to 

 fourteen flame cells observed on one side. Irregular masses of 

 reproductive system cells posteriorly located, with a row of 

 nuclei extending to a small mass anterior to ventral sucker. 

 Average length of sausage-shaped redia i.i mm., width 0.2 mm.; 

 orange-yellow pigment in wall; birth pore and two posterior 

 locomotor appendages observed only in immature rediae. Cer- 

 cariae encyst readily on glass slide, cysts averaging 142 fj. in 

 diameter, with two diametrically opposite projections. 



Cercaria quissetensis differs in a number of respects from the 

 six species reviewed by Lebour (1912), and from C. proximo, 

 and C. sagitata Lespes. 



CERCARLEUM LINTONI sp. nov. 

 (Figs. 20, 21.) 



Tailless larva, properly designated Cercariaeum; original de- 

 scription by Linton (19156), supplemented and emended in a 

 few details by this study. Average length of a number of 

 emerged larva?, killed without pressure, 230 n, width 84 /*. Very 



1 There is a possibility that the October and November infestations represent a 

 second species of echinostome. The second infestation consisted of immature 

 rcdiic only, but in October the rcdia? were filled with apparently fully formed 

 cercaria: (Fig. 12). These differ from the mature cercariae of the succeeding 

 infestations chiefly in that they are of somewhat smaller size and different shape 

 (Fig. 13), and lack cystogenous material. This is not considered as sufficient to 

 differentiate them into two species. 



