LOCOMOTION IX SURIRELLA. I49 



time. With this material, renewed when necessary, the avail- 

 able time of some months past has been spent in following 

 the liviny; and moving cells, and in attempts to demonstrate 

 structure and mechanism. A number of significant observa- 

 tions were made upon the others, but the apparently conclus- 

 ive facts uncovered have to do with Siirirella. 



One may observe as best he can. for hours together, this 

 large and beautiful diatom performing its rather fantastic 

 evolutions under a water-immersion objective without a cover- 

 glass, or under an oil-immersion and a coverglass, or in any 

 other way he pleases, without once seeing a sign of motion or 

 structure within the keel ^K. Figure I), except only that the 

 fibrous protoplasm of the rib-canals may now and then seem 

 to extend some little way into the keel. It all seems very 

 mysterious, the more so since extraneous particles keep travel- 

 ling intermittently back and forth along the cleft of the keel. 

 Meantime the diatom is awhile upon its valve, after which it 

 njlls gradually over to reveal its girdle, and then slowly ele- 

 vates itself upon one end. All this time, it may be believed, 

 some focussing is required, both of the eye and of the micro- 

 scope. After a long course of this the question still remains 

 — how to see the living protoplasm performing these its func- 

 tions ? For in despite of anything that has been said by any- 

 one, the feeling grows with the study, until it becomes a kind 

 of firm conviction, that all the varied little happenings of the 

 Siirirella s motion are but so many characteristic operations 

 of that familiar, but forever mysterious substance, the proto- 

 plasm, in direct action upon the surroundings through the 

 keel-cleft. But if the protoplasm is in the cleft, it certainly 

 is in the tube of the keel. Still — how to see it ? 



Here it is necessary to state that I find a difficulty in 

 understanding how Lauterborn could see anywhere in Siiri- 

 rella a webby structure of the protoplasm on the scale depicted 

 in Figure I. He calls it very obviously coarsely fibrous- 

 honeycomb structure {g7ob fibrilldrwabig ) . Biitschli himself 

 has also mentioned these rib-strands as offering a clear illus- 



