INFUSORIA. 415 



in which these minute creatures appear in vegetahle in- 

 fusions has been made the subject of careful inquiry. Mr. 

 Samuelson, whose researches on this point were carried on 

 in conjunction with Dr. Balbiani of Paris, and confirmed 

 by him, tells us that when a carefully prepared infusion of 

 vegetable matter in distilled water is exposed to the air, 

 the Protozoa which first appear in it are Amoeba? : these in 

 a few days disappear, and are succeded by ciliated infusoria, 

 such as Kolpoda, Cyclidium glaucoma, and sometimes Vor- 

 ticella, and these in their turn by what we have looked 

 upon as higher forms, Oocytrichum, Euplotes, Kerona, &c. 

 Mr. Samuelson thinks that Monads are but the larval con- 

 dition of the ciliated infusoria, and he noticed the constant 

 occurrence of Monads belonging to the species Circomonas 

 fusiformis, or acuminata of Dujardin, &c, in pure distilled 

 water after a certain exposure to the air, and this without 

 the previous admixture of vegetable matter of any kind in 

 the water. The same results were obtained upon shaking 

 rags, from various and distant parts of the world, over the 

 distilled water ; in all cases in about three weeks he 

 invariably obtained forms of ciliated infusoria. " The fusi- 

 form body of the Circomonas bears a long whip-like cilium 

 at its anterior end, and a short seta at its caudal extremity : 

 this finally drops off, and when exposed to excessive heat 

 and light, the animal is transformed into an Amoeba." 



Mr. Samuelson's results do not very materially differ 

 from our own, save in one or two particulars. The suc- 

 cession of generations do not take quite the same course, 

 and the animal and vegetable bodies generally appear 

 simultaneously, or so soon after each other that it is at 

 times difficult to decide the priority of appearance ; but 

 our experiments have been chiefly confined to collections 

 of rain and distilled water, witlwut the addition of vege- 

 table matter of any kind. We are, however, quite agreed 

 as to the very extensive distribution of these infusorial 

 germs, and their great tenacity of life. With regard to the 

 supposed purity of rain-water, at no time can it be taken 

 without the numerous matters floating in the air being 

 brought down with it ; and, consequently, within a few hours 

 after it is caught, Protococcus pluvialis, Amoeba, and Circo- 

 monas may always be found in vast numbers. It is somewhat 



