DESCRIPTION OF PLATES. 817 



Fig. 11. Infrabuccal apparatus of female (iV". viacromphalus) in state of erection. It 

 seems likely that the tentacles of this organ take an active part in fashioning the outer 

 capsule of the egg. (Cf. figg. 2 a and 6« of this plate.) 



Fig. 12. Infrabuccal organ (organ of Van der Hoeven) of the youngest male {N. pompilius) 

 obtained, x 20. 



Fig. 13. One of the outermost digital tentacles, to show the protuberant ridges towards 

 the apex, x 2. 



Fig. 14. Portion of an ophthalmic tentacle showing ciliated lamellae. (Reduced from 

 figure published in Quart. J. Micr. Sci. 1897.) . . 



PLATE LXXX. {N. pompilius.) 



Figg. 1 and 2. Views of the right (1) and left (2) extrabuccal series of tentacles in 

 the youngest male obtained. The ventral group of four tentacles represents the spadix or 

 the anti-spadix, but is, at this stage, exactly equal on both sides of the cephalopodium. 



«. Cut edge of ventral symphysis. 



Fig. 3. Young (sinistral) spadix showing unmodified apices of the tentacles protruding 

 from their sheaths, x 3. 



[The middle length of the hood of the original specimen was about 33 mm., and width, 

 measured over the eyes, about the same.] 



The letter g is placed upon the sheath of the first tentacle or ijlans of the spadix. 



i. Cut edge of intercoronal membrane which was removed in order to expose the entire 

 spadi.x which was sunk deeply behind it. 



s. Cut edge of ventral symphysis. 



Fig. 4. Outer aspect of same, showing f. the free tentacle of the spadix, partially 

 concealed behind the membranous e.xpansion of the sheath of the glans. 



Fig. 5. The same, with sheaths of tlie tentacles laid open and the free tentacle {/.) cut off. 

 g. Glans. 



Fig. 6. Another (dextral) spadix rather older than preceding, showing commencing 

 reduction of the apical portion of the glans (g.). 

 f. Free tentacle of spadix. 



Figg. 7 and 8. Spadix (7) and anti-spadix (8) of an older specimen (middle length of 

 hood nearly 40 mm., width across the eyes about 38 mm.), x 3. 



The free tentacle of the spadix is, at this stage, the most prominent member of the series. 



i. Cut edge of intercoronal membrane. 



s. Cut edge of ventral symphysis, with the nineteenth digital tentacle of the outer 

 whorl of the cephalopodium, beside it. 



Fig. 9. Inner surface of the ventral symphysis of a young female (measuring 66 mm. 

 from the root of the siphuncle to the anterior border of the hood), showing the commencing 

 formation of the lamellae of the organ of Valenciennes. Natural size. 



Fig. 10. The right extrabuccal lobe of the same specimen; free dorsal border on tlie 

 left, cut edge below and on tlie right of the figure. The tentacles have attained their normal 

 development (compare figg. 1 and 2). x 2. 



