MÉMOIRES. 17 



their cells. In Surirella splendida, they are very nu mé- 

 rous, and the smaller globules exbibit an active rotatorv 

 motion throughout ihe central portion of the valve. 



To thèse tVagmentary observations, I bave only to add 

 tbat tbey were eonducted under a magnification of f'rom 

 one to two tbousand diameters. Tbe objectives employed 

 were respectively, n° 8 Hartnack, l / l0 ib Ross, '/, 6 U ' Gund- 

 lacb, water immersions. A y,, 1 * bomogenous immersion 

 lens was also used, but in no way did it materially assist 

 my observations. Tbe illumination was lamp-light and a 

 Ross achromatie-eondenser ; day-light, sun-ligbt, when 

 it eould be got, modified and toned down by interposing 

 eoloured glass and monocbromatic fluids. 



