fn.^ 



rm. 



brn. oe. dig-gl- 

 rad. V ^ \ 



sh. 



St. 



Fig. 402. Diagrammatic median sections through A, Nautilus and B, Sepia 

 for comparison of the organization of the Tetrabranchiata and Dibranchiata 

 respectively. Altered from Naef. brn. brain; cm. caecum; ct. ctenidia; 

 dig.gl. digestive gland ; fn. funnel ; g.sep. genital septum ; h. heart ; ho. hood ; 

 i.s. ink sac;y. jaws; k. kidney; Ip. lips; mt. mantle; mt.' dorsal extension in 

 Nautilus; o. ovary; oe. oesophagus; rad. radula; rm. rectum; sep. septa; sh. 

 shell; sip. siphuncle; st. stomach; t. testis. Sepia is shown in the expiratory 

 position with the mantle pressed against the funnel, and the valve of the latter 

 flat against its wall. In the inset C, the inspiratory phase is seen with the 

 mantle relaxed to allow the entry of water as shown by the arrow, and the 

 valve of the funnel opened so as to prevent the passage of water. 



