546 Mr. Sanmclson on the Development of certain Infusoria. [Dec. 7, 



glycogen, and a plant with its blanched starch-storing tissues, is striking 

 in many ways. May not " migration," which plays so important a part in 

 vegetable physiology, occur in the animal economy in reference to other 

 substances besides fat? 



IV. " On the Development of certain Infusoria." By J. SAMUEL- 

 SON, Esq. Communicated by WILLIAM CHOOK.ES, Esq. Re- 

 ceived November 8, 1865. 



(Abstract.) 



The chief object of this paper is to account in some degree for the suc- 

 cessive appearance, in organic infusions, of what seem to be distinct 

 species of Protozoa rising in the developmental scale ; but the author com- 

 mences with some general remarks on the origin of these animalcules, nnd 

 states, among other conclusions at which he has arrived, his disbelief in 

 spontaneous generation as it is understood by Pouchet and his disciples. 



Proceeding to the immediate purpose of the paper, the author first refers 

 to the well-known fact, that when an infusion of decaying organic matter 

 is exposed to the air, the types of Protozoa which first appear in it are 

 the so-called Monads, and occasionally the particles of organized protoplasm 

 known as Amoeba, but that these in a few days in great part disappear, and 

 are succeeded by ciliated infusoria, such as Kolpoda, Cyclidium, Glaucoma, 

 and sometimes Vorticella oftentimes followed in their turn by other 

 types, as Oxytrichum, Euplotes, Kerona, &c. This phenomenon, he re- 

 marks, has been accounted for in different ways ; but his own observations 

 and experiments justify, in his opinion, the conclusion that the monadine 

 form which first appears is the earlier or larval stage of at least one, if 

 not more of the ciliated infusoria, into which it becomes metamorphosed 

 in the progress of development. In the first place, he states that he and 

 Dr. Balbiani have observed the regular occurrence of monads belonging 

 to the species of Cercomonas fusiformis or acuminata of Dujardin, in pure 

 distilled water which has been exposed some time to the atmosphere. 

 These, or their zoospores, would seem to be wafted by the air along with 

 particles of dust to which they cling. They readily appear when dust is 

 sifted into distilled water, and in this way have been obtained from 

 different localities at home, and, along with other forms, in dust shaken 

 from rags imported from various distant parts of the world. An experiment is 

 then related, conducted by the author during the hot weather of last summer, 

 in which a comparison was made between the animalcules which made their 

 appearance in a vessel of pure distilled water exposed to the air, and those 

 successively appearing in distilled water to which extract of lettuce had 

 been added. In both liquids Cercomonades speedily showed themselves; but 

 whilst they remained unchanged in form in the pure water till near the 

 end of the experiment (a period of about three weeks), they entirely dis- 

 appeared from the lettuce-infusion in six or seven days, and were sue- 



