XII 



PHYLUM MOLLUSCA 



Internally the lamellae are not completely in contact, an axial 

 .canal being left through which the water penetrates freely to all 

 parts of the gill. The blood carried to the gill by the afferent 

 branchial vessel passes in a system of minute branches through 



. 620. Sepia cultrata, lateral dissection of male. The left-hand half of the head has 

 been removed by an approximately median longitudinal section, the buccallfmass, however, 

 being left intact ; the funnel and the anterior and posterior walls of the mantle-cavity are 

 likewise bisected longitudinally. The left ctenidium with the left nephridial sac and 

 left branchial heart have been removed from their natural position and displaced backwards 

 so as to expose the other organs. The liver with its ducts and the pancreatic appendages 

 have been removed, but the position of the liver is indicated by a dotted line. app. appendage 

 of left branchial heart ; itort. aorta ; aort'. aboral aorta ; buc. buccal mass ; br, cart, section of 

 cartilage supporting the arms ; cer. g. cerebral ganglia ; giz. gizzard ; ink s. ink -sac ; inf, 

 funnel ; jaic, jaw ; t. aur. left auricle ; /. br. ht. left branchial heart ; L cten. left ctenidium ; 

 liv. position of liver ; /. neph. left iiephridial sac ; n. cart, nuchal cartilage ; m. oesophagus ; 

 of. cavity of otocyst laid open ; peiL g. section of pedal ganglion ; perist. peristomial mem- 

 brane ; post, c. abdominal vein ; r. aur. right auricle ; r. cten. right ctenidium ; rcct. rectum ; 

 >>"./. sulivary gland ; $h. shell ; st. stomach ; te. testis ; ra. valve of funnel ; r. car. vena cava ; 

 rent, ventricle. 



the lamellae, and is gathered up again into vessels which open into 

 the main efferent vessel leading to the auricle 



Nervous system. Though parts homologous with those of the 

 nervous system of Triton are recognisable in that of. Sepia their 

 proportions and arrangement indicate a higher grade of organisation. 



