52 ILLINOIS BIOLOGICAL MONOGRAPHS [270 



to Notocotylus aegyptiacus ; it differs, however, from this species in the 

 relative length of the cirrus pouch and vagina. In the position of the 

 genital pore it agrees with Notocotylus seineti Fuhr. and in this respect it 

 differs from other known species of this genus. 



Stages in the Life History 



Three collections No. 5769, 5770, and 5771 of the United States 

 National Museum contain immature forms of this species. Collection No. 

 5771 contains both immature and sexually mature worms. The very young 

 stages found in the two collections from the muskrat agree so well with 

 the immature forms from Aix sponsa that it is impossible to differentiate 

 the two forms and consequently they are taken to be identical. 



The most immature specimens have apparently just burst out of the 

 cysts since the pigmentation can be seen quite as perfectly as in most 

 Notocotylid oercariae. The pigmentation in this species agrees generally 

 with that described by Cort (1914) for Cercaria urbanensis. The pig- 

 mentation remaining is arranged around the lateral eye spots (Fig. 19) and 

 the lateral pigmented lines extending from the eye spots to near the 

 posterior end. Aside from this there is a very diffuse pigmentation through- 

 out the entire body. From the time of encystment of the cercaria to the 

 youngest stages at hand considerable change has taken place. The 

 anterior eye spot has been lost and the general pigmentation as described 

 above is generally much reduced as compared with the heavily pigmented 

 Cercaria urbanensis. The locomotor pockets have been resorbed so that 

 no trace of them exists in the youngest stages at hand. Development of 

 the ventral glands is the most conspicuous change which has taken place. 

 Figure 14 shows diagrammatically the youngest stage studied in which 

 three ridges or keels are thrown out on the ventral side. The median one 

 being about twice as high as the lateral ones which are ventral in position 

 to the intestinal crura (Fig. 12). Along the median ridge the papillae 

 altho only partially differentiated are clearly seen. The lateral ridges 

 show indistinct irregularities which in section are clearly the beginnings 

 of the papillae. No trace of the outer rows of papillae which occur in 

 Notocotylus quinqueserialis have been observed. In more mature stages 

 the ventral papillae are distinctly seen (Figs. 17, 19). 



Faust (1918) stated that in the Monostomata the paired ceca are 

 filled with a jell and are nonfunctional in the cercaria stage. In contrast 

 to this the ceca in the youngest stages studied, which are of course well 

 past the cercaria stages Faust studied, show that changes have taken 

 place in this feature. The ceca in these stages show the intestine as a tube 

 (Fig. 12) whose walls are surrounded by large nucleated cells. Totos in 

 this stage of development also show distinct but small internal and external 

 diverticula (Fig. 19). 



