APPENDIX. 227 



on than cover the bodies, which have a pair of lobes, 

 around which vibrate minute cilia in snch a manner 

 as to give them an appearance of rotatory motion. 

 Under a lens "they may be seen moving about very 

 actively in various positions, but always with the 

 look of being moved by rapidly turning wheels. We 

 should have been glad to witness the next step 

 towards assuming their ultimate form, but were disap- 

 pointed, as the embryos died. Fig. 2 / is the tongue 

 of a Nassa, from a photograph by Dr. Kingsley. 



