VII. 



Some Recent Researches on the Movements 



of Diatoms. 



'l^HE announcement a short time ago of the discover}^ of supposed 

 ^ pseudopodial processes in Diatoms by Mr. J. G. Grenfell, in 

 the Quarterly jf our mil of Microscopical Science (October, i8gi) has excited 

 much criticism from various sides, some of which may be found 

 summed up in a short note on the subject in Natural Science for 

 April, 1892 (p. 94). In the words of Mr. Jabez Hogg, quoted in that 

 notice, the processes in question "are, in no sense of the word, 

 pseudopodia, neither are they, nor can they be regarded as, organs 

 of locomotion ; and their discovery — which, by the way, is a very 

 aged one — throws no light whatever on the debatable question : the 

 movements of diatoms." 



In March of this year a paper was read by Professor Blitschli, of 

 Heidelberg, before the " Naturhistorisch-Medizinischer Verein " of 

 that University, containing a preliminary account of some researches 

 carried on by himself and a student, Herr Lauterborn, upon the 

 movement of a large species of Diatom.' The results obtained are 

 so novel and important that, from this reason, as well as from the fact 

 that the journal in which they are published is one not easily acces- 

 sible to English readers, no further excuse is needed for bringing them 

 before the notice of the general scientific public. 



The researches in question were conducted on a large species of 

 Pinmilaria, which Herr Lauterborn identified as P. nobilis. M. 

 Schultze had already shown that in various Diatoms foreign bodies 

 could often be seen gliding along the so-called raphe in the middle 

 line of the side of the shell, and concluded from this and other 

 observations that the shell valves could be opened for a longer or 

 shorter distance along the course of the raphe, and that here the 

 protoplasm, which plays a part in the movement, comes to the surface. 

 This observation was frequently repeated, and finally the authors 

 were able to obtain more exact results by placing specimens of 

 Pinmilaria nobilis into water containing Indian ink. By careful 

 observation of the Diatom in side view, it could be seen that at the 

 ends of the raphe nearest to the so-called nodtili in the middle of 



1 Verhandl. Nalurhist.-Med. Vereins zu Heidelberg, n.s., vol. iv., p. 5. 



