VARIATION AND REGENERATION. 



811 



its hold upon the shell, Nautilus can project its body from the shell with a darting 

 movement and protrude the buccal cone so as to seize hold of its food. I have seen 

 it seize a prawn between its jaws in this way, and it would not be a difficult matter 

 for a female to bite into the hood of a male. However this may be, the point to 

 which I desire to draw attention is that the wounds heal up at the edges, but the 

 parts are not regenerated. 



Table of Variations. 



Sex 



Spadix 



Siphuncular artery 



Colour of Renal Concretions 



1. 



$ 



Sinistral 



Sinistral 





2. 



„ 



Sinistral 



Sinistral 





3. 



„ 



Dextral 



Dextral 





4. 



„ 



Sinistral 



Sinistral 





5. 



„ 



Sinistral 



Dextral 





6. 



„ 



Sinistral 



Dextral 





7. 



„ 



Sinistral 



Dextral 





8. 



„ 



Sinistral 



Sinistral 





9. 



„ 



Sinistral 



Dextral 





10. 



,. 



Sinistral 



Sinistral 





11. 



? 







Sinistral 





12. 



„ 







Dextral 





13. 



»» 







Dextral 





14. 



6 



Dextral 



Median 





15. 



» 



Dextral 



Dextral 





16. 



3 



Sinistral 



Dextral 



Faint roseate (Rose-white) 



17. 



? 







Dextral 



Rose-white 



18. 



6 



Dextral 



Dextral 



Dark crimson 



19. 

 20. 



" 



Sinistral 

 Sinistral 





White 

 Light scarlet 







Amphioxus is another example of a relatively fixed type which presents little range 

 of variation, and less power of regeneration. Perhaps Chiton is another. 



Sometimes the sheaths of the tentacles become perforated at some part of their 

 length, and the tentacle may then issue from the adventitious orifice instead of from 

 the apical orifice. 



Not seldom among the shells of N. pompilius which are washed upon the reefs 

 of New Guinea specimens are found in which the umbilicus is incompletely closed 1 . 



1 I have figured some examples of this umbilical aberration in Quart. J. Micr. Sci., xxxix., figures on 

 PI. 13, 1896, pp. 227—230. 



w. vi. 106 



