1894.] MICROSCOPICAL JOURNAL. 241 



firmness or stiffness of structure like the pseudopodia of 

 any of the globose or villose amoeba. ^ 



In certain large fossil specimens of Navicula nobilis, 

 I have been enabled to recognize the siliceous raphe pro- 

 jecting above the valvular faces, and vanishing or taper- 

 ing off on their entrance into the nodular cavity. This 

 cavity is grossly evident in Navicula dariana, and clearly 

 enough in all of the larger species of Navicula. In the 

 dried and mounted, larger Naviculse of these studies, the 

 solid projections of whatever there may be of a raphe 

 or keel thereon, does not show in the least in frustules 

 showing their front (sutural) faces. Hence it may safely 

 be assumed for the purpose of the hypothetical discussion 

 of the same, that the raphoid alate projecting processes, 

 are protoplasmic appendages of the diatom and that they 

 vanish when the frustule dies, or is cleaned for mount- 

 ing. All the leading motile phenomena referred to here- 

 in, have their corresponding analogies among the ad- 

 mitted or acknowledged Rhizopods and the Forameuiferal 

 members of the orders of the Protozoa. 



In addition to the various motile aspects of the diatom 

 in its sutural, non-travelling aspect, I will include two 

 additional phases that I witnessed. I have seen a straight 

 line of black pigment ejected at right angles to the nodule, 

 and after a pause sucked back out of sight, the line of 

 pigment being asJong as twice the width of the frustule, 

 and also a continuous ejection of the black current from 

 a nodule and slowly coming up and away as a black 

 close spiral. The coils widened as the ejection of pig- 

 ment was kept up. But there was not going on at the 

 same time the formation of the sigmoid lines of granules. 



In the initial experiments with Prussian blue the 

 rapid formation of drifts or cloudlets of snow-like tufts 

 interfered with the inspection of the sigmoid lines, and 

 resulted in my settling upon India ink for the final tests. 

 In the material last used, I found living Navicula, after 



