1899] Microscopical journal. dl 



complete failure at once, as none of the diatoms in them 

 lived longer than two or three weeks. In the vials they 

 did better, some of them remaining alive two years after- 

 ward, but development was checked. They simply exist- 

 ed in much the same condition as when placed in the vial. 

 In two or three, however, some individually increased in 

 size until they were at least twice as large as the rest. 

 After this, there was little change for some time. I tested 

 these larger ones with acids. A very faint, shadowy and 

 flaccid membrane of silex remained. In the original ves- 

 sel the film soon showed traces of the attacks of de- 

 structive animals. Colonies of minute naviculoid dia- 

 toms, of Amphora and Nitzschia formed and grew rapid- 

 ly and then the whole film would become detached and 

 slide down to the bottom. 



One of these cultures was of material from the Quinnip- 

 iac marshes. This developed abundance of Melosira bor- 

 rerii. With this was Nitzchia reflexa in condition similar 

 to the N. closterium before described, but the frustules 

 were about twice as large, and had sufficient silex to show 

 a faint and feeble skeleton after treatment with acid. I have 

 found the rocks in Morris creek above the dike covered 

 with a growth of Melosira borrerii in which the filaments 

 averaged over six inches in length. Detached patches form- 

 ed rounded masses sometimes a foot in diameter, resembling 

 in appearance a commercial sponge. 



Taken from the water they collapsed into a rope of harsh 

 feeling filaments without any elasticity. The harsh feel was 

 caused by independent diatoms and other organisms adher- 

 ent to and entangled among the filaments. The adherent 

 diatoms were often Pleurosigma, the specimens of the small 

 "Pleurosigma paradoxum, H. P." described and figured by 

 Peragallo in his monograph, were taken from a clump of 

 Melosira from Morris creek. It may seem an extreme view 

 to class these microscopic filaments of the culture, with the 

 other comparatively gigantic growths, but the change from 



