62 



COMPARATIVE ANATOMY 



senting the outer and inner lamellae are also united from place 

 to place by hollow outgrowths called inter-lamellar junctions. 



ci- 



*? 



B 



Fig. 14 



A. Diagram of the hinder face of a single gill filament otMytilu* cdulis* 

 dl, descending limb of the filament ; asl, ascending limb ; //', inter- 

 lamellar junctions ; ci, ciliated junctions. B. Vertical section 

 through the body of Anodonta. cygnea in the posterior region of 

 the foot. PC, pericardial cavity; V, ventricle; Au, auricles; R, 

 rectum wrapped round by the ventricle ; VC ', vena cava below the 

 pericardial floor; Ur, ureter or non-glandular part, and gl, glan- 

 dular part of the excretory orpin ; Sb.p, supra-branchial passages ; 

 OG, outer gill plate ; 1G, inner gill plate ; M, mantle ; M', 

 thickened muscular border of the mantle ; /, intestine, of which 

 there are several coils in the foot. (Z>, original ; A after Holman 

 Peck.) 



which clearly correspond to the vertical partitions connecting 

 the outer and inner laminae in Anodonta (fig. 13, A). By 



