310 Microscopic Life, [Sess. 



is seen obliquely, its cylindrical character is at once recog- 

 nised. In order to test whether the organism was really a 

 diatom, and had a silicified covering, we endeavoured to crush 

 some specimens between two slides, and although the experi- 

 ment was a difficult one on account of the small size of the 

 filaments, and of the fact that the surfaces of the slides are 

 not exactly plane, we satisfied ourselves that some of the cells 

 were fractured, and not simply crushed as a vegetable tissue 

 would be. It was evident from comparison of different fila- 

 ments that each cell frequently divides into two, but we have 

 not succeeded in seeing exactly how this takes place. In fact, 

 there are many things about the organism that we find very 

 puzzling. This much is certain, that the globes appear upon 

 the thinnest filaments, from which it would seem that new 

 cells are formed inside the old ones, and are therefore of less 

 diameter ; and so on from time to time, until a stage is 

 reached when no further cell-division takes place. It appears 

 that when the filaments have reached a certain stage of growth, 

 the endochrome in some of the cells becomes green, but our 

 observations have not enabled us to say definitely what then 

 takes place. 



Desmids are beautiful objects, but we have not come across 

 very many except at Strath peffer, where there were great 

 numbers. Some of them were very large, and, except for 

 their bright green colour, closely resembled ornamental dish- 

 papers. Closteria, which belong to Desmidiese, may be found 

 anywhere : they are usually crescent-shaped, and often look 

 like tiny cucumbers. I am afraid we have been rather lazy 

 in regard to Desmids, for we have not identified a single one ! 

 We were for a long time anxious to find Volvox ; but as we 

 were unable to do so, we wrote to Mr Bolton, who advertises 

 in ' Nature,' and obtained some specimens from him. The 

 winter before last Mr Thomas Scott advised us to fish for it in 

 the Elf Loch. We did so in faith, and when we examined our 

 collection that evening we were delighted to see a large number 

 of these lovely organisms. They are perhaps more fascinating 

 to watch than any other microscopic object, owing to their 

 graceful motion and exquisite structure. They seem to be 

 very fragile, and our specimens disappeared entirely in two 

 days, leaving, as Shakespeare says, " not a wrack behind." The 



