1894.] MICROSCOPICAL JOURNAL. 197 



Smith's important and interesting observation of the for- 

 mation of tlie balls of indigo particles, was an incidental 

 outcome of the experiment designed to determine the 

 presence or absence of the investing gelatiDous ectodenn 

 of the diatoms; and the results of the experiments with 

 indigo water-color liquid, as recorded and illustrated in 

 both papers, aid in confirming and corroborating some of 

 the results previously made known by Dr. Ehrenberg in 

 his experiments on the injesting by infusoria and dia- 

 toms, of pigmentary particles, added to the waters in 

 which they were'studied and cultivated. As a conse- 

 quence of what Ehrenberg had noted through this 

 method of research, he decided that the Bacillariacese or 

 DiatomacesB were many stomached and were therefore 

 classed by him among the Polygastrica (Infusorians), 

 and thus placed under animal organisms. After his day, 

 a school of English observers gradually beat down this 

 classification, and eventually succeeded in having their 

 views take precedence over Ehrenberg's; it is thus, as an 

 outcome of change of views, through a species of mental 

 evolution, that in the published volumes of the Challen- 

 ger Expedition, if one desires to investigate the Diato- 

 macese encountered on this three years voyage, and taken 

 from the surface down to the abyssal depths of the great 

 oceans, he will find in the volumes devoted to botany, 

 the fruits of that expedition as worked up by the Count 

 Abbe Castracane. 



In Castracane's paper entitled " Greneralites relating to 

 the DiatomacesB," he is absolutely silent as to the motil- 

 ity of the exoplasm or protoplastnic covering of any of the 

 tnotile genera, and while he notes and calls attention to 

 the backward, forward, and hesitating movements 

 of the motile diatoms ; he does not analyse the motion 

 deeply and suggests that their motion is probably due to 

 the drawing in and exuding of water from opposite ends 

 of the frustule. This was his view as published (1884), and 



