417 



Some Points in the Structure and Life-History of 



Diatoms. 



By F. R. Rowley, F.R.M.S. 



Communicated hy D. J. Scourjield, F.B.M.S. 



{Read January \&th, 1903.) 



Plate 23. 



In " Natural Science'' for December, 1898, pp. 406-416, 1 gave 

 a somewhat full account of the movement of Diatoms and the 

 structure of the frustules in two forms, viz., Pinnularia nmjor 

 and Surirella calcarata, based upon Robert Lauterborn's "Unter- 

 suchungen liber Bau, Kernteilung undBewegungder Diatomeen."* 

 The interesting sections dealing with the protoplasm and its 

 inclusions, the nucleus, the centrosome, and the phenomena 

 attending nuclear and cell division, were left untouched owing to 

 lack of space, but I propose in the present paper to partly 

 supply this deficiency. Although several years have elapsed 

 since the publication of Lauterborn's work, there are doubtless 

 many who have not had an opportunity of becoming acquainted 

 with his researches, and may, therefore, be glad to avail them- 

 selves of the present abstract. 



It was in the summer of 1 891 that Lauterborn first commenced 

 to work at the Diatom aceae, in order to discover, if possible, the 

 relation of the centrosome, discovered by Biitschli in Surirella 

 calcarata, to the dividing nucleus. 



On the approach of winter, when the species just mentioned 

 became increasingly scarce, he extended his observations to other 

 and more easily procurable forms, such as Nitzsckia, Pleurosigma, 

 Pinnularia, Navicula, etc., obtaining in all cases most interesting 

 results. 



* Engelmann, Leipzig, 1896. 



