252 OILMAN A. DREW. 



PLATE XX. 



FIG. 7. A portion of a gill showing the arrangement of parts. The figure indicates 

 the inter-lamellar junctions cut at different levels. The further lamella is the one 

 that was attached to the suspensory membrane and the vessel (f>a / ) was directly con- 

 nected with the vessel that supplied the gill with blood (&a, Fig. l). This vessel 

 follows along the edge of the inter-lamellar junction to the free edge of the unattached 

 lamella (the one on the side nearest the observer in the figure), where it bends back 

 and passes down the modified filament as the vessel ba ff . Branches are given off 

 from this vessel through the inter-filamentar junctions to supply the filaments. The 

 vessel bv' is the vessel into which the blood that has traversed the gill is collected. 

 It in turn communicates with the vein of the gill (bv, Fig. l). Magnified about 

 seventy diameters. 



ba> ', branch of the branchial artery; ba" ', branch of the branchial artery in the 

 modified filament ; bv' ', branch of the branchial vein ; ft; chitinous rod ; gf, gill 

 filament ; ifj, inter-filamentar junction ; ilj, inter-lamellar junction ; io, inhalent 

 ostium. 



