482 



Mr. Wesche asked if the method by which diatoms moved had 

 really been discovered. 



The President said this was a question not easily answered with 

 certainty, as various reasons had been assigned, and the question 

 appeared to have been lately reopened. 



Mr. Scourfield said there was now an idea that it was due to 

 the projection of an extremely hyaline substance from the central 

 node of the diatom. He thought that recent investigations such 

 as those of Lauterborn appeared to indicate that they were on 

 the right track towards the discovery of the cause of diatom 

 movement. 



Mr. Morland said that the emission of a hyaline substance 

 was mentioned some time ago by Professor Hamilton Smith, who 

 observed it in the case of some diatoms mounted in a medium, 

 which showed the hyaline substance very clearly along the 

 raphe. 



Mr. Earland asked why it had not been possible for this 

 substance to be stained and shown if it really existed ? 



Mr. Scourfield said he thought it was probably due to the 

 fact that workers had hitherto taken very little trouble to 

 investigate the living diatom, nearly lall their efforts having 

 been concentrated on the shapes and markings of the " cleaned " 

 frustules. 



Mr. Karop said that this question of the emission of a hyaline 

 substance by diatoms went back as fai' as Ehrenberg, and, though 

 much had been written on both sides, he was not at all convinced 

 that there was conclusive evidence that anything of the sort 

 existed. In defence of Ehrenberg it should, however, be said 

 that he did his work with lenses of a most inferior description. 

 As they knew, he bought a microscope for 10 thalers, and they 

 might form some idea of the quality of an instrument at that 

 price in his time. 



Mr. Scourfield presented the first part, dealing with Cladocera, 

 of a paper entitled " A Synopsis of the Known Species of British 

 Fresh-water Entomostraca," proposing to follow up the subject 

 if possible by papers on other groups later on. Professor W. 

 Lilljeborg has recently recorded about ninety-six species of 

 Cladocera as having been found in Sweden, and his work, 

 " Cladocera Sueciae," will no doubt form the basis for most 

 subsequent work on the subject. Of the ninety-six Swedish 



