1900] MICROSCOPICAL JOURNAL 101 



Evolution of the Bacillaria. 



ARTHUR M. EDWARDS, M.D., F.L.S. 

 NEWARK, N.J. 



I wish to set down in brief, so that it may be readily 

 understood, what I judge was the evolution of the Bacil- 

 laria — in short, how the Bacillaria, that is to say the 

 DiatomaceaB, came first, for they were the first to appear. 

 That is why we find their remains back in the oldest rocks, 

 for they have been found in the Lower Silurian. Evolu- 

 tion took place in them as it did once in all living things, 

 and it does now ; and I wish to state my knowledge of it, 

 but it is by no means perfect. It is the knowledge of one 

 who has acquired it in over forty years hard study, — 

 study pretty constantly applied to the knowledge of them; 

 first as animals, then as vegetables, and lastly as Protista, 

 through the stimulus given to me by Bailey, Walker-Ar- 

 nott and Brightwell. 



The ordinary cell of a Bacillarian is a sphere, or rather 

 was a sphere. For that is the shape that a mass of gel- 

 atinous matter assumes, when left to itself. Fluid also 

 assumes that shape. Now what is the shape of a Bacil- 

 larian ? It appears in various forms. But the commonest; 

 and one of the first to appear in spring, when the cold 

 has broken up and the matter of the Bacillarian has a 

 chance to form, is nearly a sphere. I mean what is known 

 as Cyclotella. It was also one of the first to be named. It 

 had been named by C.A. Agardh,in the Botanische Zeitung 

 for 1827, Frustulia, from the Latin meaning little pieces 

 or fragments. But F. T. Kutzing in his Synopsis Dia- 

 tomacearum, in 1833, thought it looked like a little disc, 

 which it does on one view,and gave it the name of Cyclo- 

 tella from the Greek. Ehrenberg,inthe Abhandlungen de 

 Berlin Akademie, changed it to Pyxidicula from the Greek 

 name of a box. And now we see that it is a box when 

 viewed on the front side, the top and bottom of the box 



