CONTEXTS 



Page 

 VII— POST-LARVAL, FIXED, OR SPAT STAGES 



Difficulty of Discovery when Very Young 52 



Use of Glass Strips as Cultch 54 



Attachment to Natural Majiine Objects 55 



Dimensions of Newly Fixed Spat 56 



References to the Spat 56 



VIII— ORGANS OF THE SPAT 



The Shell 58 



The Velum 61 



The Foot 63 



Method of Fixation : Byssus Gland 64 



The Mantle 66 



Adductor Muscles 67 



Gills 67 



Phylogeny of the Lamellibranchiate Gill 70 



The Intestinal System 71 



Mouth and Palps 71 



The Nervous System. 74 



Heart 74 



Nephridia 74 



Reproductive Organs 75 



