Bull. U. S. B. F., 1921-22. (Doc. 922.) 



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m 



156 



--K 



---GF 



157 



158 



Fig. 155.— Transverse section through the pericardial elands. X 350 approximately. OS. blood corpuscle; Ep, epi- 

 thelium of the pericardial gland; A/v, muscle fibers (After Grobben, 1S8S.) 

 Fir,. 156. — Pericardial gland epithelium drawn from life. X 490. (After Grobben, 1888.) 

 Fig. 157— Photomicrograph of a transverse section taken through the anterior region of the kidney. ABV. afferent 



branchial vein, Br, gill, EBV, efferent branchial vein; A', kidney; L, liver; M, mantle. 

 Fig. 15S.— Photomicrograph of a longitudinal section through the genital papilla. X 12. EG, excretory opening; GC, 

 genital canal; GF, genital follicle filled with ova; GO, genital opening; A', kidney 



