1897] MICROSCOPICAL JOURNAL. 35 



also that the entire epidermal coat may be actively en- 

 gaged in gathering up any character of minute mineral 

 or other debris along its path. Huch particles as become 

 attached, are independently moved from numerous cen- 

 ters of vital action. This is as if the epidermal surface 

 at any given point had a retractile and contractile powei-, 

 independent of any other given point of vital action along 

 the frustuiar surface. The motile functions consist of 

 the power of transporting small mineral particles such 

 as sand grains and vegetal debris for appreciable dis- 

 tances along its edges or surface, and of rejecting then] 

 and substituting new particles. Tlie particles may be 

 jerked up at any point and carried indifferently in a posi- 

 tive or negative direction from the point of attachment, 

 until these particles are replaced by new ones. It shoald 

 strike any observer who may verify these phases of ac- 

 tion that such phenomena point to a more complex cilia- 

 like function tiian that which may be noted in the ciliary 

 fringes of an oyster or clam. The latter cilia motion 

 lashes and drives the particles in a general direction or 

 current. The complicated system of moving particles 

 can also be followed in its interminable variations as long 

 as it may suit the convenience of the observer to change 

 the specimen of Nitzschia uiideir observation, on account 

 of its relatively conspicuous size. Nitzschia scalaris is a 

 very satisfactery species in which to study the character 

 of its vital movements. 



The internal frustuiar contents present an abundance 

 of globular bodies of varying sizes which have a constant 

 independent motion among themselves, that is, their juxta- 

 position is seen to be constantly changing when very 

 carefully noted. 



Nitzschia scalaris when viewed under a power of 500 

 di'uneters is longer than any other of the North Ameri- 

 can specimens of the bacillar forms, and therefore can be 



