Cu oc 



164 



OpN 



[65 



167 



PAd CVC 



168 



Fig. 164.— Cross section through a pallial sense organ. X 575. Fixed in Gilson fluid and stained with Delaneld hematoxylin. 

 Cu, cuticula; IC t inner cilia; N, nerve supplying the sense organ; OC, outer cilia. 



Fig. 165. — Cross section of anal epithelium. X i.ooo. Preparation same as fig. 164- BBC, basal bodies of cilia; C, cilia 

 PgG, pigment granules. 



Fig. 166. — Transverse section through eye of young mussel 15 mm. long. X soo. Fixed in Flemming fluid and stained with 

 Heidenhain iron haematoxylin and congo red. Ln, so-called lens; OpN, optic nerve; PEp, pigmented epithelium of eye cup. 



Fig. 167.— Cross section through body epithelium containing two pinsehellen of Flemming. X 1,000. Preparation same as 

 fig. 166. CEp, ciliated epithelium, Pn, pinselzellen of Flemming. 



Fig. 168. — Lateral view of anterior end of gills with superior palp reflected to show position of eye at base of first filament of 

 inner gill lamella. By, byssus; DP, descending portion of outer gill lamella, E, eye; Ft. foot; IG, inner gill lamella; IP, inferior 

 palp; M, mantle; Mth, position of mouth; OG, outer gill lamella; SP, superior palp. (Alter Pelseneer, 1899.) 



Fig. 169. — Cross section passing through posterior adductor muscle to show positionsof abdominal senseorgan and osphradium 

 in relation to roots of gill. X 50. Preparation same as fig. 166. ASO, abdominal sense organ; Br, gill; CVC, cerebro visceral 

 commissure; M, mantle, OS. osphradium; PAd, posterior adductor muscle. 



178 



