89 
Text-Fic, 4. Structure of the Gills: 
x R Post-trematicus dorsalis JX 
7 Branchial arch. 
_fEfferent branchial! vessel. 
wR Pre-trematicus primus X. 
__--R Post-trematicus ventralis IX. 
AE ae Afferent branchial vessel 
blige ets ae Base of gill ray. 
_- Filamenter muscle 
2 
~>=~ Afferent-~ 
filamentar vessel. 
Capillary plexus. 
woe resee ny 
wonwenesneenennanennem-----Gill ray. 
-=--=----.--~-~------Efferent filamentrar vessel: 
Ext Int. 
: Gill ray. 
: Capillary plexus 
we 
Vascular lamella. 
A. Diagrammatic transverse section through BranchialZarch I. B. Trans- 
verse section of a double filament, showing the surfaces of two lamelle, 
C, Longitudinal section of a single filament in a plane at right angles to A, 
