no palmer: 



the path of the frustule is thinly strewn with it, whether or 

 not it collects into filaments as in Pinnularia ; and so the 

 living substance protects itself against too rough an environ- 

 ment, making a safe and smooth pathway as it goes, like the 

 snail or slug crawling forever upon its own slime. The raphe 

 stream may be mostly coleoderm in bulk, but one cannot rid 

 himself of the picture of the plasma stream deep within, the 

 living soul of all the mechanism. 



And however this may be, and in fact whatever Lauter- 

 born's view has of adequacy or inadequac}' in explanation of 

 the forward crawling of Plnyiularia , unfolding streams of col- 

 eoderm, however vigorous, seem altogether to fail in clearing 

 up other aspects of the problem, as seen in other species. 

 Even in Pinmdaria itself, one is unable to see how the frus- 

 tule that has fallen on its side is ever going to right itself 

 upon its raphe with Lauterborn's machinery. But it does so 

 with some machinery. Not easily nor quickly, nor without a 

 struggle indeed ; but in the end the thing is accomplished. 

 It is as if invisible, mysterious tentacles were put forth, which 

 with much eflFort, and often after a few failures, succeeded at 

 last in rolling the frustule into position. And Eiinotia, an 

 arcuate parallelopipedon, when fallen on its convex girdle, 

 rotates smoothlj^ and with celerity through i8o° of arc, so 

 bringing itself right side up for crawling purposes. Above 

 all, the wonderful phenomena of Bacillaria paradoxa are to 

 be explained, not by the action of an unfolding film of coleo- 

 derm, which is a practically impossible thought, but alto- 

 gether satisfactorily by simultaneous currents rotating in the 

 same direction in adjacent cells, and by consequence in oppo- 

 site directions in keels in mutual contact. But the rifted keel 

 structure of the Bacillaria frustule is as the structure in 

 Nitzschia generally ; and broadly the same may be said of 

 Siirirclla, where independently these rotating currents are 

 made evident by particles sticking to the coleoderm in the rift 

 of the keel and traveling along it. 



With all due deference, I would point out that it has been 



