LIST OF TEXT FIGURES. 



Page. 



1. Diagram of an hypothetical primitive mollusc 5 



2. Sagittal section of an embryo; modified from Koeschelt & Heideb 5 



3. „ „ ,, a later embryo; „ „ „ , 6 



4. „ „ „ an adult squid , . . . . 6 



5. The nuchal cartilage 15 



6. Lateral view of an adult squid 16 



7. Diagram of the muscles of the fin. 17 



8. Section of fin 18 



9. Ring of an unsymmetrical sucker 22 



A. upper aspect. 



B. lateral aspect. 



10. Muscles of the siphon, from above 23 



11. The jaws 31 



A. upper mandible. 



B. lower „ 



C. jaws articulated. 



12. Three rows of radular teeth 33 



13. Pseudopodial (?) rectal cells *1 



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 ... 68 



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. 



