a septate desmosome. Small calcium-rich granules fill intercellular spaces 

 and are present in small vesicles in apical cytoplasm and microvilli. 

 Amoebocytes in subepithelial connective tissue also contain granule-filled 

 vacuoles. Soluble Ca was detected histochemically in intercellular spaces 

 but not intracellular ly. These characteristics, and paucity of rough 

 endoplasmic reticulum and Golgi complexes are characteristic of cells in ion 

 or water transporting epithelia. Cells of the outer epithelium of the mantle 

 were almost devoid of mineral ash. Most ash in the mantle was associated with 

 granules in the subepithelial connective tissue and intercellular spaces. It 

 is assumed that the main pathway of Ca permeation through mantle epithelium 

 is via intercellular spaces. The outer epithelium of the mantle has little 

 or no transepithelial ionic and osmotic gradient and relatively small 

 electrical potential. In Mercenaria Ca appears to move across the outer 

 epithelium of the mantle in 2 forms. Mineral-rich granules react with sodium 

 fluoride and probably represent a complex between an organic substrate and 

 Ca. A soluble sulphated acid glycoprotein in the shell matrix binds Ca 

 selectively and tightly. The mineral-rich granules may represent this Ca- 

 glycoprotein complex. If so they probably represent less than 10% of the Ca 

 traversing the mantle. The granules appear to originate in close association 

 with amoebocytes in subepithelial connective tissue, and to move up the 

 intercellular spaces to the level of the septate desmosomes, eventually to be 

 extruded through the microvilli into the extrapallial cavity. Much of the Ca 

 moves through the epithelium in soluble ionized form. The main route of Ca 

 permeation through the outer epithelium of the mantle is via intercellular 

 spaces. The paracellular route does not preclude some role for epithelial 

 cells themselves in generation or control of Ca fluxes. Some component of 

 outward Ca flux could be coupled with inward K transport or outward movement 

 of C0 2 . - J.L.M. 



1376 



Nelson, Julius. 1910. 



Report of the biologist. In Annual Report N.J. Agric. Coll., Exper. Sta. , 

 New Brunswick: 225-266, 5 pis. 



Some clam larvae are noted in table 2 (presumably hard clam larvae, but not 

 identified) which lists oyster larvae obtained by water filtration. - J.L.M. 



1377 



Nelson, Julius. 1911. 



Report of the biologist. In Annual Report, N.J. Agric. Exper. Sta., New 

 Brunswick: 185-217. 



Mevoenavia (Venus) mercenaria is not mentioned. - J.L.M. 



1378 



Nelson, Julius. 1913. 



Report of the biologist. In Annual Report, N.J. Agric. Coll., Exper. Sta., 

 New Brunswick: 281-345. 



In the Mullica River in 1912 large numbers of clam "fry" were observed in the 

 plankton on 4 August. These were particularly abundant at the surface in a 

 "tide slick". A Connecticut oysterman told the author that such slicks were 

 the place to look for oyster "fry". This and other reports in this series 

 contain detailed observations on weather, temp, tides, salinity, and abundance 

 of oyster larvae. - J.L.M. 



387 



