EXCRETORY SYSTEM IN DIGENEA. 339 



from each side. Flame cells consisting of five paired groups on 

 each side of body. 



A few large germ-gland cells located ventral to bladder. 



SUMMARY. 



1. The number and distribution of groups of flame cells is the 

 fundamental basis of structure of the excretory system of the 

 distomes. Number of flame cells in each group and total number 

 of flame cells are of secondary significance. 



2. The group of flame cells is typical of all members of a family 

 or at least of a subfamily. 



3. The basic flame-cell group of each family or subfamily 

 may be expressed as a general formula. Substitution in this 

 general formula for the exact number of flame cells in each group 

 shows variations within individual units, which, in each case, 

 are multiples of the common denominator on which the general 

 formula is based. 



4. Seven new species of distome cercarise are described, which 

 are of special importance in affording evidence of the orderliness 

 of the excretory system of the Digenea. 



REFERENCES CITED. 

 Cort, W. W. 



'18 Homologies of the Excretory System of Forked-tailed Cercariae. Jour. 



Parasit., 4, 49-57, 2 figs. 

 Faust, E. C. 



'17 Notes on the Cercariae of the Bitter Root Valley, Montana. Jour. Parasit., 



3, 105-123, i pi. 

 '18 Life History Studies on Montana Trematodes. 111. Biol. Monogr., 4, 



1-120, 9 pi. 



'i8a Studies on Illinois Cercariae. Jour. Parasit., 4, 93-110, 2 pi. 

 Looss, A. 



'94 Die Distomen unserer Fische und Frosche. Bibl. Zool., 16, 1-296, 9 Taf. 

 '96 Recherches sur la faune parasitaire de 1'Egypte. Mem. 1'institute Egyp- 

 tien, 3, 1-252, 16 pi. 



