LIST OF TEXT FIGURES. 



1. Diagram of an hypothetical primitive mollusc, 



2. Sagittal section of an embryo; modified from Koesohelt & Heider, 



3. „ „ „ a later embryo; 



4. „ „ „ an adult squid . 

 ■5. The nuchal cartilage. 



6. Lateral view of an adult squid - 



7. Diagram of the muscles of the fin. 



8. Section of fin 



9. Ring of an unsymmetrical sucker . 



A. upper aspect. 



B. lateral aspect. 



10. Muscles of the siphon, from above 



11. The jaws 



A. upper mandible. 



B. lower „ 



C. jaws articulated. 



12. Three rows of radular teeth 



13. Pseudopodial (?) rectal cells . . - ' 



I. from a squid 2 cm. long. 

 II. „ adult squid. 



14. Model of the forward (proximal) portion of the lumen of the third gland (blind sac) of the 

 seminal vesicle 



A. from outer side. 



B. „ behind (in section). 



15. Diagram of the oesophageal, buccal, and brachial nerve rings, seen from the side 



16. Photographs of the giant nerve cells 



A & B. two adjacent sagittal sections of the pedal ganglion. 



C. transverse section of the pedal ganglion. 



D. median sagittal section of the visceral ganglion. 



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