56 ILLINOIS BIOLOGICAL MONOGRAPHS [56 



may be scattered around the ganglia altho not imbedded in the fibers. In 

 the redia of C. trisolenata the fibers are less conspicuous than the ganglion 

 cells. Species closely related may have cells of different numbers and different 

 sizes. In C. micropharynx there are always just two ganglion cells, imbedded 

 in the fibers, just above the esophagus. Their nuclei are large, pyriform, 

 and usually containing conspicuous refractory nucleoli. They measure 5. 5/li 

 to 6fx in short diameter by 8.5^ to 9/i in long diameter. The nucleoli are 

 about 2fx in diameter. Cercaria glandulosa presents a case where there is a 

 definite number of minute gangUon cells within the ganglion masses. There 

 are fifteen cells in each of the two masses. The cell walls are not well defined, 

 but the nuclei are readily distinguished. They measure l/x to l.S^t in short 

 diameter by 1.5ju to 2^1 in long diameter. The ganglion cells of C. pellucida 

 are numerous; it has not been ascertained whether they are constant in num- 

 ber. They are subspherical at times, but are usually multipolar. The entire 

 cell averages Z.Sjj. by 6^ while the nuclei measure Iju to 1.6/i. The cells of the 

 redia of C. trisolenata are usually multipolar in the region of the epidermis. 

 They range from 6/i to 22/i in diameter. The nuclei are inconstant in size, 

 varying from 2ju to 6)u in diameter. The nuclei of the ganglion cells of C. 

 gracillima are so minute in the nerve complex in the germ balls (Fig. 151) that 

 they are barely visible under 1,000 magnification. Yet these nuclei are 

 definitely set off from the surrounding matrix. They measure about 0.4/i 

 in diameter. 



In cell-studies of adult trematodes the nerve cells have been measured in 

 many cases. The measurements range from 80/i (Lejtenyi, 1881:41) in Gas- 

 trodiscus polymastos to 6;u (Fischer, 1883:17) in Opisthotrema cochleare. The 

 nuclei range from 12)U (Juel, 1889:41) in Hemiurus excisus to 1.6ijl in Opistho- 

 trema cochleare (Fisher). A comparison of these measurements in adult 

 trematodes with those for the cercariae, shows that the nuclei of the adult 

 cercariae are as large as those of the adult trematode. It is evident, however, 

 that the cells are much smaller in the cercariae. Ageing of these cells consists, 

 then, in the growth of the cytoplasm rather than an increase in size of the 

 nucleus. 



